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Groups > comp.graphics.apps.gnuplot > #3681

Undefined value during function evaluation

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Gnuplot always ansers with this problem:
Current data point
=========================
#               = 31 out of 55
x               = 100000         
z               = 225            

Current set of parameters
=========================
a               = 100000         
b               = 0.00015        
d               = 30             

         "Einzelspalt.plt", line 10: Undefined value during function evaluation



My input is:

a=100000
b=0.15e-3
c=633e-9
d=30
e=880
f(x)=((a)**2)*((b)**2)*((c/(pi*b*sin(atan((x-d)/e))))**2)*((sin((pi*b*sin(atan((x-d)/e)))/c))**2)
fit f(x) 'Einzelspalt.txt' using ($1):($2) via a,b,d
plot f(x), 'Einzelspalt.txt' using ($1):($2)

If I comment the fit out, gnuplot plots the Funktion f(x) with the values for a,b,c,d,e that I have definied before. And it also plots the data of "Einzelspalt.txt". I tested it with a polynomial as f(x), what makes no physikal sense, and it worked. Gnoplot fitted that polynomial to my data and gave me the values.
Because it prints the function in case that I don´t want to fit it, I think gnuplot also "understands" f(x).
So I can not imagine what the problem is. Could anyone help me, please?

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Undefined value during function evaluation schmidtanna114@gmail.com - 2017-06-27 06:54 -0700
  Re: Undefined value during function evaluation Karl Ratzsch <mail.kfr@gmx.net> - 2017-06-27 18:01 +0200
  Re: Undefined value during function evaluation schmidtanna114@gmail.com - 2017-06-27 12:40 -0700
  Re: Undefined value during function evaluation Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2017-06-27 21:44 +0200
  Re: Undefined value during function evaluation schmidtanna114@gmail.com - 2017-06-28 07:16 -0700

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