Hello,
I'd like to represent some 4D data and am having trouble convincing
gnuplot to do it. The data consists of locations in a 3-dimensional
volume, e.g. (r, theta, phi), with a value associated with each
location. I'd like gnuplot to make a 3D scatter plot, color each point
according to its value, and display a color scale. From the manual it
seemed like the way to do this would be:
set cbrange [range of values]
set log cb
to color points on a log scale, and then use palette cb to make the
colors go as I want:
splot "density31.dat" using 1:3:2 with points lt palette cb $4
(if you're curious, the positions are actually in spherical coordinates
using a slightly different mapping than the one in gnuplot, hence the
out-of-order columns.)
The problem is that palette cb will apparently only take a constant
value as an argument, so the command above fails, giving me an
"undefined value" error on the argument to palette cb. (The command
works fine if I replace the column argument $4 with a constant value,
but then all the points are the same color.) I can probably come up
with a way to use "rgb variable" to do this, but then I don't get a
color scale.
There were several similar questions to this already on the newsgroup
but most of them had either no response or a minimal (and pessimistic
one). Is there a way to get the output I want from gnuplot (maybe with
rgbformulae?) or should I give up and use a different program?
I have limited access to the newsgroup but if I am able to work out the
method of doing this I'll summarize it and document it on my personal
website and post a link to the group, so please reply by email to me.
Thanks very much,
R
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