Fit with numerical integration and global variables

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Tue, 01/17/2017 - 10:56 am

I am trying to write a fit function that requires numerical integration of a function with three parameters: one fixed, one fit parameter, and the integration variable. I noticed that Integrate1D can only call user functions with a single local variable, and others need to be passed as global variables. Will it cause problems that one of my fit parameters is a global variable?

Thank you.
You should not have a problem.

Suppose you have a fitting function that has two fitting variables w[0] and w[1]. Suppose further that w[1] is involved in the integration function. Your fitting function will look like this:
Function integrationFitFunction(w,x) : FitFunc
    Wave w
    Variable x
   
    return myIntegrationFunction(w,x)
End

Function myIntegrationFunction(w,inX)
    Wave w
    Variable inX
   
        // assuming you are in root: create the global and set its value.
    Variable/G param1=w[1]
    // e.g., integrating from 0 to 1 the integrand shown below.
    return w[0]+Integrate1D(integrationFunction,0, 1)
End


Function integrationFunction(inX)
    Variable inX
   
    NVAR param1=root:param1
    // return the integrand expression using inX and param1,
    // e.g. for a simple param1*inX
    return param1*inX
End


I hope this helps,

A.G.

January 17, 2017 at 03:15 pm - Permalink