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Mathematica

Fitting Compiled function

Al Guy

Posted 11 years ago

I am trying to fit data with a compiled function, however I receive error message, I don't understand why: dat = Join[Table[{RandomReal[], RandomReal[]}, {i, 10}], Table[{RandomReal[{1, 2}], RandomReal[{1, 2}]}, {i, 10}]]; kk = Compile[{{a, _Real}, {b, _Real}, {x, _Real}}, a + b x] NonlinearModelFit[data, kk[a, b, x], {a, b}, x] CompiledFunction::cfsa: Argument a at position 1 should be a machine-size real number. >> Any ideas how to fix it? Thanks!

I am trying to fit data with a compiled function, however I receive error message, I don't understand why:

dat = Join[Table[{RandomReal[], RandomReal[]}, {i, 10}], 
   Table[{RandomReal[{1, 2}], RandomReal[{1, 2}]}, {i, 10}]];
kk = Compile[{{a, _Real}, {b, _Real}, {x, _Real}}, a + b x]
NonlinearModelFit[data, kk[a, b, x], {a, b}, x]

CompiledFunction::cfsa: Argument a at position 1 should be a machine-size real number. >>

Any ideas how to fix it? Thanks!

POSTED BY: Al Guy

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Al Guy

Posted 11 years ago

I see, thanks.

POSTED BY: Al Guy

David Reiss

David Reiss, Scientific Arts

Posted 11 years ago

In the course of executing within NonlinearModelFit the function kk is being evaluated with symbolic arguments, hence the warning message. The way to avoid the warning message is not to use a compiled function in this case. However, you still get a result (and the correct one) because when a CompiledFunction encounters a case where the arguments supplied to it are not numerical it will default to evaluating with the original expression. So one way to fix this is to wrap your kk with Quiet ;-) as in NonlinearModelFit[dat, Quiet[kk[a, b, x]], {a, b}, x] Basically you tell it to shut up.

POSTED BY: David Reiss

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