Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.graphics.apps.gnuplot > #364

Re: trying to get a fit to work.

Show all headers | View raw

On 08.06.2011 01:32, aviphysics wrote:
> So I got this HPLC peak that I am trying to fit a exponentialized
> Gaussian to. It fits decently in Mathematica but trying to fit it in
> gnuplot yields "Undefined value during funtion evaluation"

> Any ideas what the problem might be?

It's exactly what the message says it is: that function's value is not 
defined over the entire of the range you're trying to use it in.  This 
show up if you just plot this function in gnuplot:

	p [0:160] modeltwo(x) with linespoints

Note how the curve ends around x==100, in particular:

gnuplot> print modeltwo(100)
3.16514318564887e-009
gnuplot> print modeltwo(105)

gnuplot> print modeltwo(105)
                ^
          undefined value

The ultimate reason for that is that erfc() underflows for arguments as 
large as you try to use it with here.

Back to comp.graphics.apps.gnuplot | Previous | Next — Previous in thread | Next in thread | Find similar

Thread

trying to get a fit to work. aviphysics <aviphysics@gmail.com> - 2011-06-07 16:32 -0700
  Re: trying to get a fit to work. Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2011-06-08 23:02 +0200
  Re: trying to get a fit to work. sfeam <sfeam@users.sourceforge.net> - 2011-06-08 21:48 -0700
    Re: trying to get a fit to work. Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2011-06-09 22:26 +0200
      Re: trying to get a fit to work. sfeam <sfeam@users.sourceforge.net> - 2011-06-09 18:29 -0700

csiph-web