So I want to get Critical Chi-Square Value using Significance level and Degrees of Freedom. I tried using MathNet.Numerics but couldn't find which method to use to get the Critical Chi-Square Value
This was the documentation I'm referring, any help on redirecting me to correct documentation would help.
How I calculate the value in Excel is by using the formula =CHISQ.INV.RT(A2,B2)
The function you require is InvCDF(), it is used as follows:
MathNet.Numerics.Distributions.ChiSquared.InvCDF(degreesOfFreedom, probability);
I could finally solve this problem, so I want to share how I solved it.
I used the MathNet library, and to use the same function of Excel you are providing you have to keep in mind a few things: in this library it does not exist =CHISQ.INV.RT itself, instead, in C#, you need to use InvCDF (the equivalent of =CHISQ.INV in Excel) but instead of using a probability parameter like 0.05, you have to use the opposite part of the interval (0, 1), so that parameter should be 0.95.
The logic of this is in the description of the functions in Excel.
"CHISQ.INV" description says "Returns the inverse of the left-tailed probability of the chi-squared distribution", this one is the equivalent of ChiSquared.InvCDF (C#).
"CHISQ.INV.RT" description says "Returns the inverse of the right-tailed probability of the chi-squared distribution", this one DOES NOT exist in the MathNet library.
Example:
In Excel you write
=CHISQ.INV.RT(0.05, 9)
In C# you write
ChiSquared.InvCDF(9, 0.95);
In both cases the answer will be 16.9189776
Note that the order of the parameters are switched.
I hope I could help with this.
Related
My question is pretty similar to this one and I'm afraid the answer is the same... I want to save all the shapes/images on a slide as a single png (or jpeg). Programmatically, I get as far as
slide.Shapes.SelectAll();
but don't see a way to save as image. Is this possible? If not, any other suggestions, hopfully w/ examples? (not VBA - I need to automate the whole conversion)
There was a reference to OpenXML in the other post, but I'm not even sure how to pull that in.
I don't know how you'd do this in C# but I'd guess that you'd make use of the same methods as you would with VBA, where you can do:
Activewindow.Selection.ShapeRange.Export( "c:\temp\delete-me.jpg",ppShapeFormatJPG)
ppShapeFormatJPG is a PowerPoint constant, a VBA Long = 1; IIRC that'd be an Integer in C#.
The method also can take two more optional parameters, scalewidth and scaleheight, which govern the width and height of the exported image in undocumented ways. By default, no parms supplied, I get exports at 72 dpi. Larger numbers result in higher pixel count exports but distorted proportions. I'm sure there's some strange logic to it, but it escapes me; all hints welcome!
There's a third optional parm, ExportMode. In my tests, it makes no difference whether you supply it or not, and if you do, which of the available values you choose.
I'm writing a program to process a cube using Microsoft Analysis, and I want
bit values to be shown as True/False whenever I browse the cube (lets say in Excel).
I've managed to show null values as some string using 'Unknown', but I can't figure how to do the same with the actual values.
P.S. I do not want to convert it by using a CASE query in the DSV table creation. I want it to be only at the Dimension level.
Thanks.
You might "not want" to rely on a CASE statement in the DSV, but SSAS doesn't give you any other options to achieve what you want. So hold your nose and start coding...
FWIW - I prefer a SQL View (rather than calculations in a DSV) for more re-use and easier testing.
In my project i face a scenario where i have a function with numerous inputs. At a certain point i am provided with an result and i need to find one combination of inputs that generates that result.
Here is some pseudocode that illustrates the problem:
Double y = f(x_0,..., x_n)
I am provided with y and i need to find any combination that fits the input.
I tried several things on paper that could generate something, but my each parameter has a range of 6.5 x 10^9 possible values - so i would like to get an optimal execution time.
Can someone name an algorithm or a topic that will be useful for me so i can read up on how other people solved simmilar problems.
I was thinking along the lines of creating a vector from the inputs and judjing how good that vektor fits the problem. This sounds awful lot like an NN, but there is no training phase available.
Edit:
Thank you all for the feedback. The comments sum up the Problems i have and i will try something along the lines of hill climbing.
The general case for your problem might be impossible to solve, but for some cases there are numerical methods that can help you solve your problem.
For example, in 1D space, if you can find a number that is smaller then y and one that is higher then y - you can use the numerical method regula-falsi in order to numerically find the "root" (which is y in your case, by simply invoking the method onf(x) -y).
Other numerical method to find roots is newton-raphson
I admit, I am not familiar with how to apply these methods on multi dimensional space - but it could be a starter. I'd search the literature for these if I were you.
Note: using such a method almost always requires some knowledge on the function.
Another possible solution is to take g(X) = |f(X) - y)|, and use some heuristical algorithms in order to find a minimal value of g. The problem with heuristical methods is they will get you "close enough" - but seldom will get you exactly to the target (unless the function is convex)
Some optimizations algorithms are: Genethic Algorithm, Hill Climbing, Gradient Descent (where you can numerically find the gradient)
i need to use this formula in c#, and i dont know how is the original formula.
can anyone help me?
PGTO is actually the Portuguese name for the PMT Excel function (found it out with this handy Excel function names translation!
The Microsoft.VisualBasic namespace has the Financial.PMT method, but of course you can use it in C#:
Returns a Double specifying the
payment for an annuity based on
periodic, fixed payments and a fixed
interest rate
There is a .NET opensource library called NPOI that allows you to manipulate Excel files. Unfortunately, their ShiftRows function does not adjust any cell references in formulas.
Therefore, I need to create a regex pattern to update them. Take for example a cell containing the following formula:
=(B7/C9) * (A10-B4)
I would like to bump any row references by 1 thus becoming
=(B8/C10) * (A11-B5)
Basically, I just need a pattern that will extract the numbers out into a "MatchCollection". I can do the rest.
Can anyone help?
Thanks.
Take a look at my answer to another question: Which regular expression is able to select excel column names in a formula in C#?
In that answer I match formulas and include code to increment the cell number (and column naming). Also, do a search on Excel column naming here and you'll find other ways to get the names generated or incremented. I probably could shorten the IncrementColumn MatchEvaluator's code using one of those methods but that's what I came up with at the time.
You should be very careful using regular expressions for this purpose.
Excel formulas can become very complex, especially with user-defined functions or when functions apply to ranges.
NPOI contains a Formula evaluation library and I think you should have a look at this as well - especially if the spreadsheets are out of your control.