Groups > comp.graphics.apps.gnuplot > #3444

Re: Varying colour of a line plot, using a palette

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From	Ethan A Merritt <sfeam@users.sourceforge.net>
Newsgroups	comp.graphics.apps.gnuplot
Subject	Re: Varying colour of a line plot, using a palette
Date	Thu, 10 Nov 2016 15:36:42 -0800
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Karl Ratzsch wrote:

> Am 10.11.2016 um 12:03 schrieb John Edwards:
> 
>> I was wondering if anyone can think of a neat trick to vary the color of
>> a line according to magnitude. E.g. If I plot sin(x) I'd like the color
>> to vary with signal matnitude.
>> 
>> To explain further what I am trying to do, I'd like to use a palette of
>> greens and reds so that when the signal goes over a threshold then the
>> plot would vary (slowly) from green to red to highlight specific issues.
> 
> Hm, very easy:
> 
>   set samp 800
> 
>   colourf(x) = (x<treshold) ? 0 : (x * 256) + (256 * (1-x) * 256)
> 
>   plot "+" us 1:(sin($1)):(colourf((sin($1)+1)/2)) w l lc rgb var lw 3
> 
> , where you define colourf(0<=x<1) so it returns a suitable 24 bit
> integer, corresponding to the desired rgb colour.

Or you could use a defined palette:

set palette defined (0 "black", 0.5 "black", 0.75 "green", 1.0 "red")
f(x) = sin(x) * cos(x/10)
set xrange [-20:20]
set sample 800

plot '+' using ($1):(f($1)):(f($1)) with lines linecolor palette z

	Ethan

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Thread

Varying colour of a line plot, using a palette John Edwards <johned0@gmail.com> - 2016-11-10 11:03 +0000
  Re: Varying colour of a line plot, using a palette Karl Ratzsch <mail.kfr@gmx.net> - 2016-11-10 13:37 +0100
    Re: Varying colour of a line plot, using a palette Ethan A Merritt <sfeam@users.sourceforge.net> - 2016-11-10 15:36 -0800
      Re: Varying colour of a line plot, using a palette John Edwards <johned0@gmail.com> - 2016-11-11 10:24 +0000
  Re: Varying colour of a line plot, using a palette Karl Ratzsch <mail.kfr@gmx.net> - 2016-11-10 18:32 +0100
    Re: Varying colour of a line plot, using a palette John Edwards <johned0@gmail.com> - 2016-11-11 10:23 +0000

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