gnuplot-info

[Gnuplot-info] heatmap + ternary operator problem

[atoms.h <l....@fr...>]

Maybe I don't understand the syntax right, but in priciple I get the plot to
work when I do

$ set view map
$ set xrange [60:200]
$ set yrange [0:300]
$ set cbrange [0:200]
$ splot "radET1.hdat" u 1:2:4 w image

This gives me a projection of my data to the xy-plane. Now, what I like to
do is to exclude points in column 4 which are zero, since in my plot they
have no physical meaning and should not be included in the pm3d coloring.
Therefore I thought something like

$ splot "radET1.hdat" u 1:2:( $4==0 ? 1/0 : 4 ) w image

would do the trick, but doesn't. It always gives errors like
"GNUPLOT (plot_image):  Image grid must be at least 2 x 2" or
"GNUPLOT (plot_image):  Visible pixel grid has a scan line shorter than
previous scan lines"

Mabe it isn't even possible to exclude points from grid data like this? Any
clues??
(For now I shifted the cbrange sightly to negative values)
 Thanks in advance,
Thomas
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Re: [Gnuplot-info] heatmap + ternary operator problem

[Thomas S. <t.s...@fz...>]

> ...
> $ splot "radET1.hdat" u 1:2:( $4==0 ? 1/0 : 4 ) w image
>
> would do the trick, but doesn't. It always gives errors like
> "GNUPLOT (plot_image):  Image grid must be at least 2 x 2" or
> "GNUPLOT (plot_image):  Visible pixel grid has a scan line shorter than
> previous scan lines"

'help image' says:
> ... It is assumed that the image data forms an
> equidistant sampling grid in the viewing plane along two
> ... directions.

for each grid point a value is required, so exclusion is not possible.

> Mabe it isn't even possible to exclude points from grid data like this?
> Any clues??

make the unwanted points white:

set pal mod RGB funct (gray>1./400.?sqrt(gray):1), (gray>1./400.?gray**3:1),
(gray>1./400.?sin(gray*2.*pi):1)

(you may replace 1./400. by some value smaller than your valid data)
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Re: [Gnuplot-info] heatmap + ternary operator problem

[atoms.h <l....@fr...>]

Thanks, after some further research I came to the same conclusion...

> set pal mod RGB funct (gray>1./400.?sqrt(gray):1),
> (gray>1./400.?gray**3:1), (gray>1./400.?sin(gray*2.*pi):1)

This is quite fancy! Amazing...
by now I changed the coloring to a simple gradient:
white,purple,blue,cyan,green,yellow,red
Which also works - if not as sophisticated...

Many thanks,
Thomas
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