So I have this code where you enter your "area code" and then you enter how long you would like the call to be. This is basically a simple calculator that would find the cost of how much a call would be depending on your area code. I am having trouble trying to figure out how to keep the loop running if I enter in an invalid area code. As of now if I enter in an invalid area code the entire program will just end in the command prompt. Heres the code:
using System;
using static System.Console;
namespace Chapter6._1
{
class Program
{
static void Main()
{
// array info //
int[] phoneAreacode = { 608, 414, 262, 815, 715, 920 };
double[] phoneCost = { .05, .10, .07, .24, .16, .14 };
// declaring variables //
int x;
int areaCode;
double cost = 0;
int callLength;
bool validAreacode = false;
// start of actual code //
Write("Enter in the area code you want to call: ");
areaCode = Convert.ToInt32(ReadLine());
x = 0;
while (x < phoneAreacode.Length && areaCode != phoneAreacode[x])
++x;
if(x != phoneAreacode.Length)
{
validAreacode = true;
cost = phoneCost[x];
}
if (validAreacode)
{
Write("Enter in the length of your call: ");
callLength = Convert.ToInt32(ReadLine());
double finalCost = callLength * cost;
WriteLine("Your call to area code " + areaCode + " for " + callLength + " minutes will cost " + finalCost.ToString("C"));
}
else
{
WriteLine("YOU MUST ENTER A VALID AREA CODE!");
}
}
}
}
You might wrap your Read and Check routine into another while-loop:
bool validAreacode = false;
while(!validAreacode)
{
// start of actual code //
Write("Enter in the area code you want to call: ");
areaCode = Convert.ToInt32(ReadLine());
x = 0;
while (x < phoneAreacode.Length && areaCode != phoneAreacode[x])
++x;
if(x != phoneAreacode.Length)
{
validAreacode = true;
cost = phoneCost[x];
}
else
{
WriteLine("YOU MUST ENTER A VALID AREA CODE!");
}
}
This is the simplest solution for you (not so much changes in your code required). But your code still has the problems. Your program will be crashed if user tries to print any not digit character instead of area code.
You can do a do-While here:
Basically when you do do-while you force the code on the do to be done until the condition in the while is completed. in your case, you need to add the checking of the pohne number inside the do statement, and to know if the person selected a correct value, you can do Array.FindIndex():
this will be your do-while loop, also i chaned your x for index try to use names for the variables that have some meaning. (index is not perfect anyway)
do
{
Write("Enter in the area code you want to call: ");
areaCode = Convert.ToInt32(ReadLine());
index = Array.FindIndex(phoneAreacode, w => w == areaCode);
if (index >= 0)
{
validAreacode = true;
}
else
{
WriteLine("YOU MUST ENTER A VALID AREA CODE!");
}
} while (!validAreacode);
and this will be your entire main method:
int[] phoneAreacode = { 608, 414, 262, 815, 715, 920 };
double[] phoneCost = { .05, .10, .07, .24, .16, .14 };
// declaring variables //
int index;
int areaCode;
int callLength;
bool validAreacode = false;
// start of actual code //
do
{
Write("Enter in the area code you want to call: ");
areaCode = Convert.ToInt32(ReadLine());
index = Array.FindIndex(phoneAreacode, w => w == areaCode);
if (index >= 0)
{
validAreacode = true;
}
else
{
WriteLine("YOU MUST ENTER A VALID AREA CODE!");
}
} while (!validAreacode);
Write("Enter in the length of your call: ");
callLength = Convert.ToInt32(ReadLine());
double finalCost = callLength * phoneCost[index];
WriteLine("Your call to area code " + areaCode + " for " + callLength + " minutes will cost " + finalCost.ToString("C"));
As you can see you can also remove the while you have to loop the array and the if-else for the valid codes. assuming that when the code reach that point, the area is correct.
It's a good practice to try to remove the number of if-else.
You probably need to loop the entire code section, something like this
while (true)
{
Write("Enter in the area code you want to call: ");
var input = ReadLine();
if (input == "Exit")
break;
areaCode = Convert.ToInt32(input);
x = 0;
while (x < phoneAreacode.Length && areaCode != phoneAreacode[x])
++x;
if(x != phoneAreacode.Length)
{
validAreacode = true;
cost = phoneCost[x];
}
else if (validAreacode)
{
Write("Enter in the length of your call: ");
callLength = Convert.ToInt32(ReadLine());
double finalCost = callLength * cost;
WriteLine("Your call to area code " + areaCode + " for " + callLength + " minutes will cost " + finalCost.ToString("C"));
}
else
{
WriteLine("YOU MUST ENTER A VALID AREA CODE!");
}
}
Don't forget to add a check for when user types something that's not a digit
I'm using Serial Port to get data from device in for loop iteration.
The problem is in loop iteration i need to get data from serial port, validate it and going to the next iteration.
How i can achieved this?
Here are my code :
private void processData()
{
// Loop Procedure
int x = Int32.Parse(master["Cycle"].ToString());
int y = Int32.Parse(master["MinWeight"].ToString());
// Loop for each line
for (int i = this.CLine; i < 2; i++)
{
this.CLine = i;
if (i == 0)
label15.Text = master["LLINE"].ToString();
else
label15.Text = master["RLINE"].ToString();
IDictionary<string, string> dic = (Dictionary<String, String>)master[i.ToString()];
label18.Text = this.CProcess = dic["PROCESSID"];
int z = Int32.Parse(dic["PRODLANE"].ToString());
// Loop for each sampling session (Cycle)
for (int j = this.CCycle; j <= x; j++)
{
this.CCycle = j;
// Loop for production lane
for (int k = this.CLane; k <= z; k++)
{
this.CLane = k;
label16.Text = k.ToString();
// In this section i want to send command over serial port
// get value from my device
// validate it if current weight bellow standard weight
// do it again (get data from device)
// else we can go to next iteration
while (this.CWeight < y)
{
XApi.l("xxx2 " + this.CWeight + " vs " + y + " " + k.ToString() + " " + this.isDataReady);
SendData("Q");
}
// Commit Transaction
// XDb.CommitTrans(this.CCycle.ToString(), dic["LINEID"].ToString(), this.CLane.ToString(), weight.ToString(), this.isTrialStage == true ? "1" : "0");
}
}
}
}
I've tried this
while (this.CWeight < y)
{
XApi.l("xxx2 " + this.CWeight + " vs " + y + " " + k.ToString() + " " + this.isDataReady);
SendData("Q");
}
but it seems blocked UI thread and make my application solaggy.
Anyone can give me some idea? Thanks in advance.
private void port_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
if (e.EventType == System.IO.Ports.SerialData.Eof)
return;
// If the com port has been closed, do nothing
if (!comport.IsOpen)
return;
// Update flag data received
this.isDataReady = true;
// Determain which mode (string or binary) the user is in
if (CurrentDataMode == DataMode.Text)
{
// Read all the data waiting in the buffer
string data = comport.ReadExisting();
// Update result
result += data;
if (result.Length > 16)
{
SetText(result.ToString());
}
// Display the text to the user in the terminal
Log(LogMsgType.Incoming, data);
}
else
{
// Obtain the number of bytes waiting in the port's buffer
int bytes = comport.BytesToRead;
// Create a byte array buffer to hold the incoming data
byte[] buffer = new byte[bytes];
// Read the data from the port and store it in our buffer
comport.Read(buffer, 0, bytes);
// Show the user the incoming data in hex format
Log(LogMsgType.Incoming, ByteArrayToHexString(buffer));
}
}
private void SendData(String msg)
{
this.isDataReady = false;
result = "";
if (CurrentDataMode == DataMode.Text)
{
// Send the user's text straight out the port
comport.Write(msg + "\r\n");
// Show in the terminal window the user's text
Log(LogMsgType.Outgoing, msg + "\n");
}
else
{
try
{
// Convert the user's string of hex digits (ex: B4 CA E2) to a byte array
byte[] data = HexStringToByteArray(txtSendData.Text);
// Send the binary data out the port
comport.Write(data, 0, data.Length);
// Show the hex digits on in the terminal window
Log(LogMsgType.Outgoing, ByteArrayToHexString(data) + "\n");
}
catch (FormatException)
{
// Inform the user if the hex string was not properly formatted
Log(LogMsgType.Error, "Not properly formatted hex string: " + txtSendData.Text + "\n");
}
}
}
Anyone can give me some idea?
You can use async/await in your code not to block your UI by writing an extension method like below. Usage would be:
async void SomeMethod()
{
SerialPort serialPort = .......
while (true)
{
serialPort.Write(.....);
var retval = await serialPort.ReadAsync();
}
}
The keyword here is using TaskCompletionSource class with your events...
static public class SerialPortExtensions
{
public static Task<byte[]> ReadAsync(this SerialPort serialPort)
{
var tcs = new TaskCompletionSource<byte[]>();
SerialDataReceivedEventHandler dataReceived = null;
dataReceived = (s, e) =>
{
serialPort.DataReceived -= dataReceived;
var buf = new byte[serialPort.BytesToRead];
serialPort.Read(buf, 0, buf.Length);
tcs.TrySetResult(buf);
};
serialPort.DataReceived += dataReceived;
return tcs.Task;
}
}
I'm working in C# (2013) Windows Forms. My instructor wanted us to ensure that the txtStateInput is upperCase when we hit the calculate button. However when I input a two character string such as "wi" and then hit calculate, it throws the message "enter valid state" and clears out the textbox. When I enter the "wi" in a second time then it works. I can't figure out why this is happening, the code would lead me to believe that it would check to ensure the string in txtStateInput is two characters and then when calculate is clicked it would uppercase the string. I can't figure out why it only works once I enter in the state "wi" a second time.
private void btnCalc_Click(object sender, EventArgs e)
{
//declare variables.
int startPop = 0;
int endPop = 0;
string Message = "Error";
decimal Percent = 0.0m;
string State = "";
string City = String.Empty;
int dTimes = 0;
try
{
City = txtCityInput.Text;
//System Globalization was initialized so this method works.
TextInfo myTI = new CultureInfo("en-US", false).TextInfo;
txtCityInput.Text = myTI.ToTitleCase(City);
if(txtStateInput.Text.Length != 2)
{
MessageBox.Show("Enter valid State");
txtStateInput.Focus();
txtStateInput.SelectAll();
}
else
{
State = txtStateInput.Text.ToUpper();
txtStateInput.Text = State;
if ((int.TryParse(txtStartPopInput.Text, out startPop)) && int.TryParse(txtEndPopInput.Text, out endPop))
{
if ((startPop > 0) && (endPop > 0))
{
//if population has decreased.
if ((startPop > endPop))
{
Percent = ((decimal.Parse(endPop.ToString()) - decimal.Parse(startPop.ToString())) / decimal.Parse(startPop.ToString()));
Message = "Pop. Decrease of " + Percent.ToString("p");
}
//if population has increased.
if ((startPop < endPop))
{
Percent = ((decimal.Parse(endPop.ToString()) - decimal.Parse(startPop.ToString())) / decimal.Parse(startPop.ToString()));
Message = "Pop. Increase of " + Percent.ToString("p");
}
//if population has not changed.
if ((startPop == endPop))
{
Percent = ((decimal.Parse(endPop.ToString()) - decimal.Parse(startPop.ToString())) / decimal.Parse(startPop.ToString()));
Message = "No Change in Population";
}
}
else
{
MessageBox.Show("Please enter valid population figures.");
}
}
if (int.TryParse(txtDisplayTimes.Text, out dTimes))
{
if (dTimes > 0)
{
lstResults.Items.Clear();
int iSum = 0;
int iLoopCount = dTimes;
//displays the results according to value in txtDisplayTimes.
for (iSum = 1; iSum <= iLoopCount; iSum++)
{
lstResults.Items.Add(Message);
}
}
}
}
}
catch
{
MessageBox.Show("Something went wrong.");
}
}
I'm new to threading, and I am trying to use it in a program (front end for a hardware test), but running into heavy time delays - clearly I'm doing something wrong.
My Setup:
I have a hardware controller hooked up to my PC. I am communicating with it via serial to read values from 4 sensors. This communication sits within receiveHandler,
private void receiveHandler(object sender, DataStreamEventArgs e)
{
byte[] dataBytes = e.Response;
//throws it into a string
//parses the string with delimiters
//adds all items to a linked-list "queue"
}
I have a timer (System.Timers.Timer) that will count the duration of the hardware test, do one calculation and ask the controller for the updated state of each sensor.
private void OnTimedEvent(object sender, EventArgs e)
{
test.duration = ++tickCounter;
test.ampHoursOut = (test.ampHoursOut * 3600 + test.amperage * 1) / 3600;
sendToController("CH2.GETANALOG"); //repeat this line once for each sensor
}
I currently have a BackgroundWorker that will take the data collected from the controller (that I stuck in a "queue" in receiveHandler) and comprehend it + do some calculations + update the UI.
private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
BackgroundWorker worker = (BackgroundWorker)sender;
while (!worker.CancellationPending)
{
//do a whole lot of logic
}
}
My Problem:
One of my controller inputs is reading the state of a hardware switch. I notice that there is a 5 second delay between when I hit the switch and when it's state changes on the UI.
There must be a heavy delay in my processing. I imagine BackgroundWorker isn't catching up with all of the information coming in. I'm asking for information every second (via the timer), so maybe this needs to slow down - but I would like to have information update every second to have an accurate test.
Am I using the timer, backgroundworker, and receive handler correctly? What can be done to speed up my communication + processing?
I'm a self-taught programmer and don't necessarily (as you can probably see) know all of the basic concepts. Any advice would be appreciated :)
Thanks, Julia
EDIT: Code:
//variables used (added relevant ones so code is better understood)
private static System.Timers.Timer timer;
LinkedList<string> incomingData = new LinkedList<string>();
string lastDatum = "";
/// <summary>
/// Method that is called when serial data is received from the controller.
/// The data is received in bytes, converted to a string and parsed at each "::" which represents a new message.
/// The last 'item' from the data is saved and added to the front of the next set of data, in case it is incomplete.
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void receiveHandler(object sender, DataStreamEventArgs e)
{
byte[] dataBytes = e.Response;
string data = lastDatum + System.Text.Encoding.Default.GetString(dataBytes); // reads the next available line coming from the serial port
UpdateDataTextbox(data); // prints it out for debuging purposes
lastDatum = ""; // just in case
char[] delimiters = new char[] { ':' }; // splits the data at the ":" symbol, deleting empty entries.
Queue<string> dataQueue = new Queue<string>(data.Split(delimiters,
StringSplitOptions.RemoveEmptyEntries));
while(dataQueue.Count > 1)
{
string str = dataQueue.Dequeue().Replace("\r", string.Empty).Replace("\n", string.Empty).Replace(":", string.Empty).Trim(); // remove all useless characters
if (str != "")
{
incomingData.AddLast(str); // add to a queue that can be accessed by the background worker for processing & outputting.
}
}
lastDatum = dataQueue.Dequeue(); // Last data item in a transmission may be incomplete "CH1.GETDA" and thus it is appended to the front of the next list of data.
}
/// <summary>
/// Background Worker thread will be used to continue testing the connection to the controller,
/// process messages in the incoming message queue (actually a linked list),
/// and sends new messages for updated data.
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
BackgroundWorker worker = (BackgroundWorker)sender;
while (!worker.CancellationPending)
{
if (!relayBoard.OpenConn())
{
MessageBox.Show("Connection to controller has been lost.");
testInterrupted = "Lost connection. Time = " + test.duration;
UpdateStatusText(false);
ShutErDown();
}
//update test time & Ah out
timeSpan = TimeSpan.FromSeconds(tickCounter);
UpdateDurationTextbox(timeSpan.ToString()); // update display with duration
UpdateAhTextbox(test.ampHoursOut.ToString());
/////////////////////////////////////////////////////
if (incomingData.Count > 0)
{
string dataLine = "";
try
{
dataLine = incomingData.First();
}
catch (System.InvalidOperationException emai)
{
break; //data hasn't come in yet, it will by the time this runs next.
}
incomingData.RemoveFirst();
if (dataLine.Contains("GET")) // some sensor values (analog/temp/digital) has come in
{
if (dataLine.Contains("GETANALOG")) // an analog value has come in
{
int index = dataLine.IndexOf("CH");
int pin = (int)Char.GetNumericValue(dataLine[index + 2]);
double value = 0;
int dataLineLength = dataLine.Length;
if (dataLineLength > 13) // value is appended to end of line
{
try
{
value = Convert.ToDouble(dataLine.Substring(13));
}
catch // can't convert to double
{
int index2 = dataLine.IndexOf("CH", 3);
if (index2 != -1) // there happen to be two sets of commands stuck together into one
{
string secondHalf = dataLine.Substring(index2);
incomingData.AddFirst(secondHalf);
}
}
}
else // value is on the next line
{
try
{
value = Convert.ToDouble(incomingData.First());
incomingData.RemoveFirst();
}
catch // can't convert to double
{
MessageBox.Show("Error occured: " + dataLine);
}
}
switch (pin)
{
case 1:
ReadVoltage(value);
break;
case 2:
ReadAmperage(value);
break;
}
}
else if (dataLine.Contains("GETTEMP")) // received reply with temperature data
{
int index = dataLine.IndexOf("CH");
int pin = (int)Char.GetNumericValue(dataLine[index + 2]); // using index of CH, retrieve which pin this message is coming from
double value = 0;
int dataLineLength = dataLine.Length;
if (dataLineLength > 11) // value is appended to end of line
{
try
{
value = Convert.ToDouble(dataLine.Substring(11));
}
catch // can't convert to double
{
int index2 = dataLine.IndexOf("CH", 3);
if (index2 != -1) // there happen to be two sets of commands stuck together into one
{
string secondHalf = dataLine.Substring(index2);
incomingData.AddFirst(secondHalf);
}
}
}
else // value is on the next line
{
value = Convert.ToDouble(incomingData.First());
incomingData.RemoveFirst();
}
ReadTemperature(pin, value);
}
else // must be CH3.GET
{
int index = dataLine.IndexOf("CH");
int pin = (int)Char.GetNumericValue(dataLine[index + 2]); // using index of CH, retrieve which pin this message is coming from
if (pin == 3) // only care if it's pin 3 (BMS), otherwise it's a mistake
{
double value = 0;
int dataLineLength = dataLine.Length;
if (dataLineLength > 7) // value is appended to end of line
{
try
{
value = Convert.ToDouble(dataLine.Substring(7));
}
catch // can't convert to double
{
int index2 = dataLine.IndexOf("CH", 3);
if (index2 != -1) // there happen to be two sets of commands stuck together into one
{
string secondHalf = dataLine.Substring(index2);
incomingData.AddFirst(secondHalf);
}
}
}
else // value is on the next line
{
value = Convert.ToDouble(incomingData.First());
incomingData.RemoveFirst();
}
ReadBMS(value);
}
}
}
else if (dataLine.Contains("REL")) // received reply about relay turning on or off.
{
if (dataLine.Contains("RELS")) // all relays turning on/off
{
if (dataLine.Contains("ON"))
{
for (int pin = 1; pin <= 4; pin++)
{
test.contactors[pin] = true;
}
}
else // "OFF"
{
for (int pin = 1; pin <= 4; pin++)
{
test.contactors[pin] = false;
}
}
}
else // single relay is turning on/off
{
int index = dataLine.IndexOf("REL");
int pin = (int)Char.GetNumericValue(dataLine[index + 3]);
if (dataLine.Contains("ON"))
{
test.contactors[pin] = true;
}
else if (dataLine.Contains("OFF"))
{
test.contactors[pin] = false;
}
else if (dataLine.Contains("GET"))
{
if (Convert.ToInt32(incomingData.First()) == 1)
test.contactors[pin] = true;
else
test.contactors[pin] = false;
incomingData.RemoveFirst();
}
}
}
}
}
}
/// <summary>
/// Main timer used to log the duration of the test, calculate amp hours
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void OnTimedEvent(object sender, EventArgs e)
{
test.duration = ++tickCounter;
// calculate Ah
test.ampHoursOut = (test.ampHoursOut * 3600 + test.amperage * 1) / 3600;
//read & output v, a, bms state
//sendToController("CH1.GETANALOG"); // get voltage
sendToController("CH2.GETANALOG"); // get amperage
sendToController("CH3.GET"); // get BMS state
//read & output temperature
sendToController("CH4.GETTEMP"); // get temperature
sendToController("CH5.GETTEMP");
}
I have some decimal data that I am pushing into a SharePoint list where it is to be viewed. I'd like to restrict the number of significant figures displayed in the result data based on my knowledge of the specific calculation. Sometimes it'll be 3, so 12345 will become 12300 and 0.012345 will become 0.0123. Occasionally it will be 4 or 5. Is there any convenient way to handle this?
See: RoundToSignificantFigures by "P Daddy".
I've combined his method with another one I liked.
Rounding to significant figures is a lot easier in TSQL where the rounding method is based on rounding position, not number of decimal places - which is the case with .Net math.round. You could round a number in TSQL to negative places, which would round at whole numbers - so the scaling isn't needed.
Also see this other thread. Pyrolistical's method is good.
The trailing zeros part of the problem seems like more of a string operation to me, so I included a ToString() extension method which will pad zeros if necessary.
using System;
using System.Globalization;
public static class Precision
{
// 2^-24
public const float FLOAT_EPSILON = 0.0000000596046448f;
// 2^-53
public const double DOUBLE_EPSILON = 0.00000000000000011102230246251565d;
public static bool AlmostEquals(this double a, double b, double epsilon = DOUBLE_EPSILON)
{
// ReSharper disable CompareOfFloatsByEqualityOperator
if (a == b)
{
return true;
}
// ReSharper restore CompareOfFloatsByEqualityOperator
return (System.Math.Abs(a - b) < epsilon);
}
public static bool AlmostEquals(this float a, float b, float epsilon = FLOAT_EPSILON)
{
// ReSharper disable CompareOfFloatsByEqualityOperator
if (a == b)
{
return true;
}
// ReSharper restore CompareOfFloatsByEqualityOperator
return (System.Math.Abs(a - b) < epsilon);
}
}
public static class SignificantDigits
{
public static double Round(this double value, int significantDigits)
{
int unneededRoundingPosition;
return RoundSignificantDigits(value, significantDigits, out unneededRoundingPosition);
}
public static string ToString(this double value, int significantDigits)
{
// this method will round and then append zeros if needed.
// i.e. if you round .002 to two significant figures, the resulting number should be .0020.
var currentInfo = CultureInfo.CurrentCulture.NumberFormat;
if (double.IsNaN(value))
{
return currentInfo.NaNSymbol;
}
if (double.IsPositiveInfinity(value))
{
return currentInfo.PositiveInfinitySymbol;
}
if (double.IsNegativeInfinity(value))
{
return currentInfo.NegativeInfinitySymbol;
}
int roundingPosition;
var roundedValue = RoundSignificantDigits(value, significantDigits, out roundingPosition);
// when rounding causes a cascading round affecting digits of greater significance,
// need to re-round to get a correct rounding position afterwards
// this fixes a bug where rounding 9.96 to 2 figures yeilds 10.0 instead of 10
RoundSignificantDigits(roundedValue, significantDigits, out roundingPosition);
if (Math.Abs(roundingPosition) > 9)
{
// use exponential notation format
// ReSharper disable FormatStringProblem
return string.Format(currentInfo, "{0:E" + (significantDigits - 1) + "}", roundedValue);
// ReSharper restore FormatStringProblem
}
// string.format is only needed with decimal numbers (whole numbers won't need to be padded with zeros to the right.)
// ReSharper disable FormatStringProblem
return roundingPosition > 0 ? string.Format(currentInfo, "{0:F" + roundingPosition + "}", roundedValue) : roundedValue.ToString(currentInfo);
// ReSharper restore FormatStringProblem
}
private static double RoundSignificantDigits(double value, int significantDigits, out int roundingPosition)
{
// this method will return a rounded double value at a number of signifigant figures.
// the sigFigures parameter must be between 0 and 15, exclusive.
roundingPosition = 0;
if (value.AlmostEquals(0d))
{
roundingPosition = significantDigits - 1;
return 0d;
}
if (double.IsNaN(value))
{
return double.NaN;
}
if (double.IsPositiveInfinity(value))
{
return double.PositiveInfinity;
}
if (double.IsNegativeInfinity(value))
{
return double.NegativeInfinity;
}
if (significantDigits < 1 || significantDigits > 15)
{
throw new ArgumentOutOfRangeException("significantDigits", value, "The significantDigits argument must be between 1 and 15.");
}
// The resulting rounding position will be negative for rounding at whole numbers, and positive for decimal places.
roundingPosition = significantDigits - 1 - (int)(Math.Floor(Math.Log10(Math.Abs(value))));
// try to use a rounding position directly, if no scale is needed.
// this is because the scale mutliplication after the rounding can introduce error, although
// this only happens when you're dealing with really tiny numbers, i.e 9.9e-14.
if (roundingPosition > 0 && roundingPosition < 16)
{
return Math.Round(value, roundingPosition, MidpointRounding.AwayFromZero);
}
// Shouldn't get here unless we need to scale it.
// Set the scaling value, for rounding whole numbers or decimals past 15 places
var scale = Math.Pow(10, Math.Ceiling(Math.Log10(Math.Abs(value))));
return Math.Round(value / scale, significantDigits, MidpointRounding.AwayFromZero) * scale;
}
}
This might do the trick:
double Input1 = 1234567;
string Result1 = Convert.ToDouble(String.Format("{0:G3}",Input1)).ToString("R0");
double Input2 = 0.012345;
string Result2 = Convert.ToDouble(String.Format("{0:G3}", Input2)).ToString("R6");
Changing the G3 to G4 produces the oddest result though.
It appears to round up the significant digits?
I ended up snagging some code from http://ostermiller.org/utils/SignificantFigures.java.html. It was in java, so I did a quick search/replace and some resharper reformatting to make the C# build. It seems to work nicely for my significant figure needs. FWIW, I removed his javadoc comments to make it more concise here, but the original code is documented quite nicely.
/*
* Copyright (C) 2002-2007 Stephen Ostermiller
* http://ostermiller.org/contact.pl?regarding=Java+Utilities
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* See COPYING.TXT for details.
*/
public class SignificantFigures
{
private String original;
private StringBuilder _digits;
private int mantissa = -1;
private bool sign = true;
private bool isZero = false;
private bool useScientificNotation = true;
public SignificantFigures(String number)
{
original = number;
Parse(original);
}
public SignificantFigures(double number)
{
original = Convert.ToString(number);
try
{
Parse(original);
}
catch (Exception nfe)
{
_digits = null;
}
}
public bool UseScientificNotation
{
get { return useScientificNotation; }
set { useScientificNotation = value; }
}
public int GetNumberSignificantFigures()
{
if (_digits == null) return 0;
return _digits.Length;
}
public SignificantFigures SetLSD(int place)
{
SetLMSD(place, Int32.MinValue);
return this;
}
public SignificantFigures SetLMSD(int leastPlace, int mostPlace)
{
if (_digits != null && leastPlace != Int32.MinValue)
{
int significantFigures = _digits.Length;
int current = mantissa - significantFigures + 1;
int newLength = significantFigures - leastPlace + current;
if (newLength <= 0)
{
if (mostPlace == Int32.MinValue)
{
original = "NaN";
_digits = null;
}
else
{
newLength = mostPlace - leastPlace + 1;
_digits.Length = newLength;
mantissa = leastPlace;
for (int i = 0; i < newLength; i++)
{
_digits[i] = '0';
}
isZero = true;
sign = true;
}
}
else
{
_digits.Length = newLength;
for (int i = significantFigures; i < newLength; i++)
{
_digits[i] = '0';
}
}
}
return this;
}
public int GetLSD()
{
if (_digits == null) return Int32.MinValue;
return mantissa - _digits.Length + 1;
}
public int GetMSD()
{
if (_digits == null) return Int32.MinValue;
return mantissa + 1;
}
public override String ToString()
{
if (_digits == null) return original;
StringBuilder digits = new StringBuilder(this._digits.ToString());
int length = digits.Length;
if ((mantissa <= -4 || mantissa >= 7 ||
(mantissa >= length &&
digits[digits.Length - 1] == '0') ||
(isZero && mantissa != 0)) && useScientificNotation)
{
// use scientific notation.
if (length > 1)
{
digits.Insert(1, '.');
}
if (mantissa != 0)
{
digits.Append("E" + mantissa);
}
}
else if (mantissa <= -1)
{
digits.Insert(0, "0.");
for (int i = mantissa; i < -1; i++)
{
digits.Insert(2, '0');
}
}
else if (mantissa + 1 == length)
{
if (length > 1 && digits[digits.Length - 1] == '0')
{
digits.Append('.');
}
}
else if (mantissa < length)
{
digits.Insert(mantissa + 1, '.');
}
else
{
for (int i = length; i <= mantissa; i++)
{
digits.Append('0');
}
}
if (!sign)
{
digits.Insert(0, '-');
}
return digits.ToString();
}
public String ToScientificNotation()
{
if (_digits == null) return original;
StringBuilder digits = new StringBuilder(this._digits.ToString());
int length = digits.Length;
if (length > 1)
{
digits.Insert(1, '.');
}
if (mantissa != 0)
{
digits.Append("E" + mantissa);
}
if (!sign)
{
digits.Insert(0, '-');
}
return digits.ToString();
}
private const int INITIAL = 0;
private const int LEADZEROS = 1;
private const int MIDZEROS = 2;
private const int DIGITS = 3;
private const int LEADZEROSDOT = 4;
private const int DIGITSDOT = 5;
private const int MANTISSA = 6;
private const int MANTISSADIGIT = 7;
private void Parse(String number)
{
int length = number.Length;
_digits = new StringBuilder(length);
int state = INITIAL;
int mantissaStart = -1;
bool foundMantissaDigit = false;
// sometimes we don't know if a zero will be
// significant or not when it is encountered.
// keep track of the number of them so that
// the all can be made significant if we find
// out that they are.
int zeroCount = 0;
int leadZeroCount = 0;
for (int i = 0; i < length; i++)
{
char c = number[i];
switch (c)
{
case '.':
{
switch (state)
{
case INITIAL:
case LEADZEROS:
{
state = LEADZEROSDOT;
}
break;
case MIDZEROS:
{
// we now know that these zeros
// are more than just trailing place holders.
for (int j = 0; j < zeroCount; j++)
{
_digits.Append('0');
}
zeroCount = 0;
state = DIGITSDOT;
}
break;
case DIGITS:
{
state = DIGITSDOT;
}
break;
default:
{
throw new Exception(
"Unexpected character '" + c + "' at position " + i
);
}
}
}
break;
case '+':
{
switch (state)
{
case INITIAL:
{
sign = true;
state = LEADZEROS;
}
break;
case MANTISSA:
{
state = MANTISSADIGIT;
}
break;
default:
{
throw new Exception(
"Unexpected character '" + c + "' at position " + i
);
}
}
}
break;
case '-':
{
switch (state)
{
case INITIAL:
{
sign = false;
state = LEADZEROS;
}
break;
case MANTISSA:
{
state = MANTISSADIGIT;
}
break;
default:
{
throw new Exception(
"Unexpected character '" + c + "' at position " + i
);
}
}
}
break;
case '0':
{
switch (state)
{
case INITIAL:
case LEADZEROS:
{
// only significant if number
// is all zeros.
zeroCount++;
leadZeroCount++;
state = LEADZEROS;
}
break;
case MIDZEROS:
case DIGITS:
{
// only significant if followed
// by a decimal point or nonzero digit.
mantissa++;
zeroCount++;
state = MIDZEROS;
}
break;
case LEADZEROSDOT:
{
// only significant if number
// is all zeros.
mantissa--;
zeroCount++;
state = LEADZEROSDOT;
}
break;
case DIGITSDOT:
{
// non-leading zeros after
// a decimal point are always
// significant.
_digits.Append(c);
}
break;
case MANTISSA:
case MANTISSADIGIT:
{
foundMantissaDigit = true;
state = MANTISSADIGIT;
}
break;
default:
{
throw new Exception(
"Unexpected character '" + c + "' at position " + i
);
}
}
}
break;
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
{
switch (state)
{
case INITIAL:
case LEADZEROS:
case DIGITS:
{
zeroCount = 0;
_digits.Append(c);
mantissa++;
state = DIGITS;
}
break;
case MIDZEROS:
{
// we now know that these zeros
// are more than just trailing place holders.
for (int j = 0; j < zeroCount; j++)
{
_digits.Append('0');
}
zeroCount = 0;
_digits.Append(c);
mantissa++;
state = DIGITS;
}
break;
case LEADZEROSDOT:
case DIGITSDOT:
{
zeroCount = 0;
_digits.Append(c);
state = DIGITSDOT;
}
break;
case MANTISSA:
case MANTISSADIGIT:
{
state = MANTISSADIGIT;
foundMantissaDigit = true;
}
break;
default:
{
throw new Exception(
"Unexpected character '" + c + "' at position " + i
);
}
}
}
break;
case 'E':
case 'e':
{
switch (state)
{
case INITIAL:
case LEADZEROS:
case DIGITS:
case LEADZEROSDOT:
case DIGITSDOT:
{
// record the starting point of the mantissa
// so we can do a substring to get it back later
mantissaStart = i + 1;
state = MANTISSA;
}
break;
default:
{
throw new Exception(
"Unexpected character '" + c + "' at position " + i
);
}
}
}
break;
default:
{
throw new Exception(
"Unexpected character '" + c + "' at position " + i
);
}
}
}
if (mantissaStart != -1)
{
// if we had found an 'E'
if (!foundMantissaDigit)
{
// we didn't actually find a mantissa to go with.
throw new Exception(
"No digits in mantissa."
);
}
// parse the mantissa.
mantissa += Convert.ToInt32(number.Substring(mantissaStart));
}
if (_digits.Length == 0)
{
if (zeroCount > 0)
{
// if nothing but zeros all zeros are significant.
for (int j = 0; j < zeroCount; j++)
{
_digits.Append('0');
}
mantissa += leadZeroCount;
isZero = true;
sign = true;
}
else
{
// a hack to catch some cases that we could catch
// by adding a ton of extra states. Things like:
// "e2" "+e2" "+." "." "+" etc.
throw new Exception(
"No digits in number."
);
}
}
}
public SignificantFigures SetNumberSignificantFigures(int significantFigures)
{
if (significantFigures <= 0)
throw new ArgumentException("Desired number of significant figures must be positive.");
if (_digits != null)
{
int length = _digits.Length;
if (length < significantFigures)
{
// number is not long enough, pad it with zeros.
for (int i = length; i < significantFigures; i++)
{
_digits.Append('0');
}
}
else if (length > significantFigures)
{
// number is too long chop some of it off with rounding.
bool addOne; // we need to round up if true.
char firstInSig = _digits[significantFigures];
if (firstInSig < '5')
{
// first non-significant digit less than five, round down.
addOne = false;
}
else if (firstInSig == '5')
{
// first non-significant digit equal to five
addOne = false;
for (int i = significantFigures + 1; !addOne && i < length; i++)
{
// if its followed by any non-zero digits, round up.
if (_digits[i] != '0')
{
addOne = true;
}
}
if (!addOne)
{
// if it was not followed by non-zero digits
// if the last significant digit is odd round up
// if the last significant digit is even round down
addOne = (_digits[significantFigures - 1] & 1) == 1;
}
}
else
{
// first non-significant digit greater than five, round up.
addOne = true;
}
// loop to add one (and carry a one if added to a nine)
// to the last significant digit
for (int i = significantFigures - 1; addOne && i >= 0; i--)
{
char digit = _digits[i];
if (digit < '9')
{
_digits[i] = (char) (digit + 1);
addOne = false;
}
else
{
_digits[i] = '0';
}
}
if (addOne)
{
// if the number was all nines
_digits.Insert(0, '1');
mantissa++;
}
// chop it to the correct number of figures.
_digits.Length = significantFigures;
}
}
return this;
}
public double ToDouble()
{
return Convert.ToDouble(original);
}
public static String Format(double number, int significantFigures)
{
SignificantFigures sf = new SignificantFigures(number);
sf.SetNumberSignificantFigures(significantFigures);
return sf.ToString();
}
}
I have a shorted answer to calculating significant figures of a number. Here is the code & the test results...
using System;
using System.Collections.Generic;
namespace ConsoleApplicationRound
{
class Program
{
static void Main(string[] args)
{
//char cDecimal = '.'; // for English cultures
char cDecimal = ','; // for German cultures
List<double> l_dValue = new List<double>();
ushort usSignificants = 5;
l_dValue.Add(0);
l_dValue.Add(0.000640589);
l_dValue.Add(-0.000640589);
l_dValue.Add(-123.405009);
l_dValue.Add(123.405009);
l_dValue.Add(-540);
l_dValue.Add(540);
l_dValue.Add(-540911);
l_dValue.Add(540911);
l_dValue.Add(-118.2);
l_dValue.Add(118.2);
l_dValue.Add(-118.18);
l_dValue.Add(118.18);
l_dValue.Add(-118.188);
l_dValue.Add(118.188);
foreach (double d in l_dValue)
{
Console.WriteLine("d = Maths.Round('" +
cDecimal + "', " + d + ", " + usSignificants +
") = " + Maths.Round(
cDecimal, d, usSignificants));
}
Console.Read();
}
}
}
The Maths class used is as follows:
using System;
using System.Text;
namespace ConsoleApplicationRound
{
class Maths
{
/// <summary>
/// The word "Window"
/// </summary>
private static String m_strZeros = "000000000000000000000000000000000";
/// <summary>
/// The minus sign
/// </summary>
public const char m_cDASH = '-';
/// <summary>
/// Determines the number of digits before the decimal point
/// </summary>
/// <param name="cDecimal">
/// Language-specific decimal separator
/// </param>
/// <param name="strValue">
/// Value to be scrutinised
/// </param>
/// <returns>
/// Nr. of digits before the decimal point
/// </returns>
private static ushort NrOfDigitsBeforeDecimal(char cDecimal, String strValue)
{
short sDecimalPosition = (short)strValue.IndexOf(cDecimal);
ushort usSignificantDigits = 0;
if (sDecimalPosition >= 0)
{
strValue = strValue.Substring(0, sDecimalPosition + 1);
}
for (ushort us = 0; us < strValue.Length; us++)
{
if (strValue[us] != m_cDASH) usSignificantDigits++;
if (strValue[us] == cDecimal)
{
usSignificantDigits--;
break;
}
}
return usSignificantDigits;
}
/// <summary>
/// Rounds to a fixed number of significant digits
/// </summary>
/// <param name="d">
/// Number to be rounded
/// </param>
/// <param name="usSignificants">
/// Requested significant digits
/// </param>
/// <returns>
/// The rounded number
/// </returns>
public static String Round(char cDecimal,
double d,
ushort usSignificants)
{
StringBuilder value = new StringBuilder(Convert.ToString(d));
short sDecimalPosition = (short)value.ToString().IndexOf(cDecimal);
ushort usAfterDecimal = 0;
ushort usDigitsBeforeDecimalPoint =
NrOfDigitsBeforeDecimal(cDecimal, value.ToString());
if (usDigitsBeforeDecimalPoint == 1)
{
usAfterDecimal = (d == 0)
? usSignificants
: (ushort)(value.Length - sDecimalPosition - 2);
}
else
{
if (usSignificants >= usDigitsBeforeDecimalPoint)
{
usAfterDecimal =
(ushort)(usSignificants - usDigitsBeforeDecimalPoint);
}
else
{
double dPower = Math.Pow(10,
usDigitsBeforeDecimalPoint - usSignificants);
d = dPower*(long)(d/dPower);
}
}
double dRounded = Math.Round(d, usAfterDecimal);
StringBuilder result = new StringBuilder();
result.Append(dRounded);
ushort usDigits = (ushort)result.ToString().Replace(
Convert.ToString(cDecimal), "").Replace(
Convert.ToString(m_cDASH), "").Length;
// Add lagging zeros, if necessary:
if (usDigits < usSignificants)
{
if (usAfterDecimal != 0)
{
if (result.ToString().IndexOf(cDecimal) == -1)
{
result.Append(cDecimal);
}
int i = (d == 0) ? 0 : Math.Min(0, usDigits - usSignificants);
result.Append(m_strZeros.Substring(0, usAfterDecimal + i));
}
}
return result.ToString();
}
}
}
Any answer with a shorter code?
You can get an elegant bit perfect rounding by using the GetBits method on Decimal and leveraging BigInteger to perform masking.
Some utils
public static int CountDigits
(BigInteger number) => ((int)BigInteger.Log10(number))+1;
private static readonly BigInteger[] BigPowers10
= Enumerable.Range(0, 100)
.Select(v => BigInteger.Pow(10, v))
.ToArray();
The main function
public static decimal RoundToSignificantDigits
(this decimal num,
short n)
{
var bits = decimal.GetBits(num);
var u0 = unchecked((uint)bits[0]);
var u1 = unchecked((uint)bits[1]);
var u2 = unchecked((uint)bits[2]);
var i = new BigInteger(u0)
+ (new BigInteger(u1) << 32)
+ (new BigInteger(u2) << 64);
var d = CountDigits(i);
var delta = d - n;
if (delta < 0)
return num;
var scale = BigPowers10[delta];
var div = i/scale;
var rem = i%scale;
var up = rem > scale/2;
if (up)
div += 1;
var shifted = div*scale;
bits[0] =unchecked((int)(uint) (shifted & BigUnitMask));
bits[1] =unchecked((int)(uint) (shifted>>32 & BigUnitMask));
bits[2] =unchecked((int)(uint) (shifted>>64 & BigUnitMask));
return new decimal(bits);
}
test case 0
public void RoundToSignificantDigits()
{
WMath.RoundToSignificantDigits(0.0012345m, 2).Should().Be(0.0012m);
WMath.RoundToSignificantDigits(0.0012645m, 2).Should().Be(0.0013m);
WMath.RoundToSignificantDigits(0.040000000000000008, 6).Should().Be(0.04);
WMath.RoundToSignificantDigits(0.040000010000000008, 6).Should().Be(0.04);
WMath.RoundToSignificantDigits(0.040000100000000008, 6).Should().Be(0.0400001);
WMath.RoundToSignificantDigits(0.040000110000000008, 6).Should().Be(0.0400001);
WMath.RoundToSignificantDigits(0.20000000000000004, 6).Should().Be(0.2);
WMath.RoundToSignificantDigits(0.10000000000000002, 6).Should().Be(0.1);
WMath.RoundToSignificantDigits(0.0, 6).Should().Be(0.0);
}
test case 1
public void RoundToSigFigShouldWork()
{
1.2m.RoundToSignificantDigits(1).Should().Be(1m);
0.01235668m.RoundToSignificantDigits(3).Should().Be(0.0124m);
0.01m.RoundToSignificantDigits(3).Should().Be(0.01m);
1.23456789123456789123456789m.RoundToSignificantDigits(4)
.Should().Be(1.235m);
1.23456789123456789123456789m.RoundToSignificantDigits(16)
.Should().Be(1.234567891234568m);
1.23456789123456789123456789m.RoundToSignificantDigits(24)
.Should().Be(1.23456789123456789123457m);
1.23456789123456789123456789m.RoundToSignificantDigits(27)
.Should().Be(1.23456789123456789123456789m);
}
I found this article doing a quick search on it. Basically this one converts to a string and goes by the characters in that array one at a time, till it reached the max. significance. Will this work?
The following code doesn't quite meet the spec, since it doesn't try to round anything to the left of the decimal point. But it's simpler than anything else presented here (so far). I was quite surprised that C# doesn't have a built-in method to handle this.
static public string SignificantDigits(double d, int digits=10)
{
int magnitude = (d == 0.0) ? 0 : (int)Math.Floor(Math.Log10(Math.Abs(d))) + 1;
digits -= magnitude;
if (digits < 0)
digits = 0;
string fmt = "f" + digits.ToString();
return d.ToString(fmt);
}
This method is dead simple and works with any number, positive or negative, and only uses a single transcendental function (Log10). The only difference (which may/may-not matter) is that it will not round the integer component. This is perfect however for currency processing where you know the limits are within certain bounds, because you can use doubles for much faster processing than the dreadfully slow Decimal type.
public static double ToDecimal( this double x, int significantFigures = 15 ) {
// determine # of digits before & after the decimal
int digitsBeforeDecimal = (int)x.Abs().Log10().Ceil().Max( 0 ),
digitsAfterDecimal = (significantFigures - digitsBeforeDecimal).Max( 0 );
// round it off
return x.Round( digitsAfterDecimal );
}
As I remember it "significant figures" means the number of digits after the dot separator so 3 significant digits for 0.012345 would be 0.012 and not 0.0123, but that really doesnt matter for the solution.
I also understand that you want to "nullify" the last digits to a certain degree if the number is > 1. You write that 12345 would become 12300 but im not sure whether you want 123456 to become 1230000 or 123400 ? My solution does the last. Instead of calculating the factor you could ofcourse make a small initialized array if you only have a couple of variations.
private static string FormatToSignificantFigures(decimal number, int amount)
{
if (number > 1)
{
int factor = Factor(amount);
return ((int)(number/factor)*factor).ToString();
}
NumberFormatInfo nfi = new CultureInfo("en-US", false).NumberFormat;
nfi.NumberDecimalDigits = amount;
return(number.ToString("F", nfi));
}
private static int Factor(int x)
{
return DoCalcFactor(10, x-1);
}
private static int DoCalcFactor(int x, int y)
{
if (y == 1) return x;
return 10*DoCalcFactor(x, y - 1);
}
Kind regards
Carsten