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Re: IDL fitting of piecewise continuous function [message #76114 is a reply to message #76112]

Tue, 17 May 2011 12:53

Jeremy Bailin
Messages: 618
Registered: April 2008

Senior Member

If you define your function analogously to the example in the MPFIT code, it might look like:

FUNCTION MYFUNCT, p, X=x, Y=y, ERR=err
; p[0] is A
x_m = SOME_CONSTANT_VALUE

; x lt x_m is 1 if x<x_m and 0 otherwise
; x ge x_m is 1 if x >= x_m and 0 otherwise
model = (x lt x_m) * p[0] * x^(0.5) + (x ge x_m) * p[0] * x_m^(1.5) / x

return, (y-model)/err
END

Of course, that assumes that x_m is a constant, not a parameter - but if it's a parameter, you would just use p[1] instead of a constant value, for example.

-Jeremy.

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[Message index]

		Re: IDL fitting of piecewise continuous function By: Craig Markwardt on Tue, 17 May 2011 19:35
		Re: IDL fitting of piecewise continuous function By: Jeremy Bailin on Tue, 17 May 2011 12:53
		Re: IDL fitting of piecewise continuous function By: Sasha Singh on Tue, 17 May 2011 12:26
		Re: IDL fitting of piecewise continuous function By: Jeremy Bailin on Tue, 17 May 2011 12:24
		Re: IDL fitting of piecewise continuous function By: Jeremy Bailin on Tue, 17 May 2011 12:21

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