Fitting your own function in Igor Pro

FuncFit takes a fit function you wrote, in the shape Igor expects.

Function DoubleExp(WAVE w, Variable t) : FitFunc
    return w[0] + w[1] * exp(-t / w[2]) + w[3] * exp(-t / w[4])
End

Function FitDecay(WAVE y)
    Make/O/D/N=5 coefs = {0, 1, 0.01, 0.5, 0.1}

    FuncFit/Q DoubleExp, coefs, y /D

    Printf "fast %.4g s, slow %.4g s\r", coefs[2], coefs[4]
    return coefs[2]
End

How it works

1. The signature is fixed: a coefficient wave and the independent variable.
2. The coefficient wave you pass in holds the initial guess.
3. FuncFit then overwrites it with the answer.

Keywords and builtins used here

• End
• FuncFit
• Function
• Make
• Printf
• Variable
• WAVE
• exp
• return

The run, in numbers

Lines

12

Characters to type

294

Tokens

100

Three-star pace

85 tpm

At the three-star pace of 85 tokens a minute, this run takes about 71 seconds.

Type this snippet

Step 3 of 3 in Curve fitting, step 10 of 16 in Waves & analysis.

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