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Curve fitting Error from user made equation

Mon, 08/19/2013 - 11:36 am

I am an IGOR novice and am attempting to curve fit soil concentrations from an analytical solution to a form of the standard 1-d diffusion equation. The code I use is below.
f(Z) = .0012+((2*QWC)/(Deff))*(((sqrt((Deff*100)/pi))*exp((-Z^2)/(4*Deff*100)))-((Z/2)*erfc(Z/(2*sqrt(Deff*100)))))
return .0012+((2*QWC)/(Deff))*(((sqrt((Deff*100)/pi))*exp((-Z^2)/(4*Deff*100)))-((Z/2)*erfc(Z/(2*sqrt(Deff*100)))))

I could save and create the equation, and run it on a differnt set of data( work with concentrations in the 0.005 range). However when I run it on smaller concentrations (0.0007 range) the follow error message appeared: "expected number between 1 and 7" and it would highlight this line of code and the very last "0" in the line...FuncFit/NTHR=0/TBOX=768 walestrialfit2 W_coef wave2[0,5] /X=wave0 /D /C=T_Constraints /F={0.954000, 0}. I am not sure what is causing this error. Any help is appreciated!

hrodstein

First look at the help for FuncFit. (If you are not sure how to do this, take a break, choose Help->Getting Started, and do the first half of the Igor Guided Tour. Among other things it shows you how to find information in Igor.)

Notice that it refers you to CurveFit for a discussion of the flags. Click the link to go to CurveFit.

Scroll down to the /F flag.

Note that the legal values for the confType parameter are 1 through 7 (a sum of 1, 2 and 4 which each have a meaning as specified in the help).

August 19, 2013 at 11:49 am - Permalink