Groups > comp.graphics.apps.gnuplot > #2074

Re: change line color when plot crosses Y value

Newsgroups	comp.graphics.apps.gnuplot
Followup-To	comp.graphics.apps.gnuplot
From	"A. W. Dunstan" <no@spam.thanks>
Subject	Re: change line color when plot crosses Y value
Date	2011-02-03 12:02 -0500
References	<15c8f4bc-fd7b-4486-972d-9321f6c96c62@m27g2000prj.googlegroups.com> <j7WdnSJ9k6lXg9XQnZ2dnUVZ_tOdnZ2d@speakeasy.net> <f11293a5-d9c7-4bb6-b5be-cba14c0ee40f@m27g2000prj.googlegroups.com>
Organization	OptiMetrics, Inc.
Message-ID	<08CdncNFKaovQtfQnZ2dnUVZ_tCdnZ2d@speakeasy.net> (permalink)

Followups directed to: comp.graphics.apps.gnuplot

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ginginsman wrote:

> On Feb 1, 3:55 pm, "A. W. Dunstan" <n...@spam.thanks> wrote:
>> ginginsman wrote:
>> > I know I have seen this somewhere but cannot find it: I'd like to find
>> > a way to change the color of a plot line when it crosses a specified
>> > value of Y; blue above, red below, for example.
>>
>> > with data like this:
>>
>> > 2011/02/01-03:31   0.59
>> > 2011/02/01-09:48   9.93
>> > 2011/02/01-16:11   -0.34
>> > 2011/02/01-22:24   8.88
>> > 2011/02/02-04:18   0.44
>> > 2011/02/02-10:32   9.96
>> > 2011/02/02-16:53   -0.36
>>
>> > set xdata time
>> > set timefmt x  "%Y/%m/%d-%H:%M"
>> > set samples 1000
>> > plot 'data.txt' u 1:2 sm cspl
>>
>> > Find a way to change the curve color at any value > or < 1 (for
>> > example).
>>
>> > OSX 10.6.6
>> > GNUplot Version 4.4 patchlevel 2
>>
>> Would something like this do the trick?
>>
>> color(y) = y >= 0 ? (255*65535) : (255*255)
>> plot "data.in" using 1:2:(color($2)) with lines linecolor rgb variable
>>
>> Tweak the definition of the "color()" function to give the desired
>> colors. The one above gives me yellow for y >= 0, green for y < 0.
>>
>> (someone on this group showed me that a few years ago & it's been handy)
>>
>> --
>> Al Dunstan, Software Engineer
>> OptiMetrics, Inc.
>> 3115 Professional Drive
>> Ann Arbor, MI  48104-5131
> 
> I'm unable to reproduce Al's results.  It looks like a good solution.
> 
> Can anyone confirm for me that it works?
> If so, perhaps dump for me the terminal settings and options you are
> using?

gnuplot> show terminal

   terminal type is wxt 0

In ~/.gnuplot-wxt I've got:
raise=1
persist=0
ctrl=0
rendering=2
hinting=100

I've done output to JPG and PostScript files this way too (although it was a 
few years ago).  I'm using Gnuplot 4.2 patchlevel 3 on Fedora 10.

-- 
Al

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Thread

Re: change line color when plot crosses Y value "A. W. Dunstan" <no@spam.thanks> - 2011-02-03 12:02 -0500
  Re: change line color when plot crosses Y value ginginsman <dbh@suiattle.org> - 2011-02-03 11:57 -0800
    Re: change line color when plot crosses Y value "A. W. Dunstan" <no@spam.thanks> - 2011-02-04 10:00 -0500
    Re: change line color when plot crosses Y value ginginsman <dbh@suiattle.org> - 2011-02-03 12:14 -0800

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