Gnuplot lables in RGB colors read from data line

Question

Related to Set variable textcolor and point color with labels style in gnuplot but not quite the same. I have a set of data in the file "test.dat":

   643.8 0.09417 28.9 00  24 255 0
   483.1 0.09232 28.0 01  255 0 120
   518.5 0.08943 29.6 02  11 65 255

I want a 3D plot where the first three comlumns are interpreted as x y z coordinates and the fourth column as a label/point symbol and then I want the label color coded in RGB which should be taken from the 5. 6. and 7th column. I try this:

rgb(r,g,b) = 65536 * int(r) + 256 * int(g) + int(b)
splot "test.dat" u 1:2:3:4:(rgb($5/255,$6/255,$7/255)) with labels tc rgb variable notitle

but the labels appear in black:

What am I doing wrong?

Answer 1

You have been close, but why do you divide your column values by 255?

Some comments:

• In the example below I used, e.g. column(5) instead of the shorter $5, because in some cases you might have to escape $ and use \$5 instead. So, column(5) is longer but "universal". And instead of 5 you could also use a variable.
• it's not necessary to use int(). gnuplot will truncate.
• you can also use hexadecimal numbers 0x10000 and 0x100 to multiply your R,G,B values with (easier to remember and less prone to typos).

Script:

### variable label color from R,G,B columns
reset session

$Data <<EOD
643.8 0.09417 28.9 00  24 255   0
483.1 0.09232 28.0 01 255   0 120
518.5 0.08943 29.6 02  11  65 255
EOD

rgb(colR,colG,colB) = 0x10000*column(colR) + 0x100*column(colG) + column(colB)

splot $Data u 1:2:3:4:(rgb(5,6,7)) w labels tc rgb var
### end of script

Result: