Line plot in GnuPlot where line color is a third column in my data file?

This following works for me (gnuplot 4.4)

plot "./file.dat" u 1:2:3 with lines  palette

Hope this helps.

When I ran your code gnuplot couldn't pass the "rgb" part.

For an example of using the variable tag see the similar question: GNUPLOT: dot plot with data depending dot size

with the useful examples found here: http://gnuplot.sourceforge.net/demo/pointsize.html

All the best

Tom

plot 'foo.dat' with lines linecolor variable

or abbreviated:

plot 'foo.dat' w l lc var

This has been asked long ago, but i just had the same question. And the most suitable way to also get legend/title for "variable" colors, was:

# set this to the range of your variable which you want to color-encode
# or leave it out
set cbrange [0:1]

# define the palette to your liking
set palette defined ( 0 "#B0B0B0", 0.333 "#FF0000", 0.666 "#0000FF", 1.0 "#000000" )

# in this example, column 3 is mapped to the colors of the palette
plot "data.txt" u 1:2:3 w l lc palette z

(tested on gnuplot 4.6 patchlevel 4)