plotting Contours with non-grid data?

[Andreas Schulze]

Hi all,

is it possible to plot contour lines from following data set?
Data:

1.0000000e+03 1.0200000e+02 3.4
1.0000000e+03 7.6000000e+01 4.5
1.0000000e+03 5.1000000e+01 5.3
1.0000000e+03 2.5000000e+01 4.4

1.5000000e+03 1.0200000e+02 4.5
1.5000000e+03 7.6000000e+01 5.4
1.5000000e+03 5.1000000e+01 5.5
1.5000000e+03 2.5000000e+01 5.6

2.0000000e+03 1.0200000e+02 4.6
2.0000000e+03 1.2700000e+02 4.0

2.0000000e+03 7.6000000e+01 5.5
2.0000000e+03 5.1000000e+01 5.5
2.0000000e+03 2.5000000e+01 5.4

I have gnuplot Version 4.0 patchlevel 0.

Best regards,
Andreas

[Steve Bickerton]

Hi Andreas,

I think you'll have to change your data file to be in grid format.
I've done that in the data i'm resending below (There was an extra point
in one of the lines that the other lines didn't have ... so i commented
it out):

Then for a simple (and pretty ungly) plot, try:

gnuplot> reset
gnuplot> set view map
gnuplot> set contour
gnuplot> unset surface
gnuplot> splot 'contour.dat'

For fancier things like smoother interpolation:

gnuplot> help contour
gnuplot> help cntrparam

will get you going. To be honest, that's not many points to work with
though ...

Hope that helps,
cheers,
steve

Andreas Schulze wrote:
> 1.0000000e+03 1.0200000e+02 3.4
> 1.0000000e+03 7.6000000e+01 4.5
> 1.0000000e+03 5.1000000e+01 5.3
> 1.0000000e+03 2.5000000e+01 4.4
>
>
> 1.5000000e+03 1.0200000e+02 4.5
> 1.5000000e+03 7.6000000e+01 5.4
> 1.5000000e+03 5.1000000e+01 5.5
> 1.5000000e+03 2.5000000e+01 5.6
>
> 2.0000000e+03 1.0200000e+02 4.6

> #2.0000000e+03 1.2700000e+02 4.0

[Steve Bickerton]

... sorry ... didn't notice 'non-grid' was a critical requirement in the
subject line ... my bad. Can't help ya with that.
steve

[Pedro J Caridade]

Hi Andreas
You can use a nice feature of gnuplot: set dgrid3d.
It uses a scheme to generate a regular grid from non-grid data. After this
contour or coloring surfaces are straightforward. Read the dgrid3d to see
the parameters.
Pedro