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From: Karl Ratzsch <mail.kfr@gmx.net>
Newsgroups: comp.graphics.apps.gnuplot
Subject: Re: User function in "using" expression
Date: Wed, 28 Aug 2019 21:53:06 +0200
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Am 28.08.2019 um 21:01 schrieb layzarc@aol.com:
> I'm trying to use gnuplot to solve a specific version of the problem
>  
> 3d plot z(x,y) with x,ys subject to the constraint f(x,y)=0
>  
> The following works (the files are 0 contours captured by set table)
> 
> array n[6]
> file(i) = sprintf("coma%d.gpt",i)
> splot for [i=1:|n|] file(i) using 1:2:(0):(0):(0):(1) with vectors
> 
> but if I also do:
> 
> phi(x,y) = (1+x)/(1+sqrt(1+(x*x-1)*y))
> spher(n,x,y) = (f=phi(x,y),n2=n*n,((f-n)^2*(f-n2)*(1-y*f)-f^3)/(n2*(n-1)^3))
> splot for [i=1:|n|] file(i) using 1:2:(0):(0):(0):(spher(n[i],$1,$2)) with vectors
> 
> I get the following message:
> 
>  non-integer passed to boolean operator
> 
> What am I missing? I can provide the full file if needed.
> 
> Al
> 

gnuplot uses