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From: Roberto Guerra IDV Novi <cipitaua@gmail.com>
Newsgroups: comp.graphics.apps.gnuplot
Subject: FIT A DATAFILE THROUGH ANOTHER DATAFILE
Date: Mon, 11 Jun 2012 06:27:41 -0700 (PDT)
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Hi,

I have a curve in a datafile that is supposed to be the weighted sum
of other two curves. I wish to find the coefficients for such sum so
that curve1=curve2*a+curve3*b.
I tried with the following fit:

 fit 0.0 "< paste curve1.dat curve2.dat curve3.dat" u 1:($2-$4*a-$6*b)
via a,b

but it sticks with the "Singular matrix" error.
Is there any workaround for that?

Thanks in advance,
Roberto