Gnuplot: ContourPlot (formating to Grid Data)

Question

My Data looks like this:

2015-08-01 07:00    0.23    0.52    0.00    0.52    9   14.6    14.6 14.6   67  8.5 0.0 --- 0.00    0.0 --- 14.6    14.1    14.1    16.3    1016.2  0.00      0.0   156 0.22    156 0.0 0.00    0.0 0.003   0.000   23.9    39  9.1 23.4    0.05    23  1   100.0   1   1.8797836153192153  660.7143449269239

2015-08-01 07:01    0.25    0.53    0.00    0.53    0   14.6    14.6    14.6    67  8.5 0.0 --- 0.00    0.0 --- 14.6    14.1    14.1    16.3    1016.2  0.00    0.0 153 0.22    153 0.0 0.00    0.0 0.003   0.000   23.9    39  9.1 23.4    0.00    23  1   100.0   1   1.8894284951616422  657.3416264126714   105 73  121 163

2015-08-01 07:02    0.25    0.52    0.00    0.52    0   14.7    14.7    14.6    67  8.6 0.0 --- 0.00    0.0 --- 14.7    14.2    14.2    16.1    1016.2  0.00    0.0 139 0.20    139 0.0 0.00    0.0 0.003   0.000   23.9    39  9.1 23.4    0.00    24  1   100.0   1   1.8976360559992214  654.4985251906015

2015-08-01 07:03    0.26    0.53    0.00    0.53    0   14.7    14.7    14.7      67    8.6 0.0 --- 0.00    0.0 --- 14.7    14.2    14.2    16.1    1016.3  0.00    0.0 139 0.20    144 0.0 0.00    0.0 0.003   0.000   23.9    39  9.1 23.4    0.00    23  1   100.0   1   1.9047561611790007  652.0519661851259

2015-08-01 07:04    0.25    0.53    0.00    0.53    0   14.7    14.7    14.7    67  8.7 0.0 --- 0.00    0.0 --- 14.7    14.2    14.2    16.2    1016.3  0.00    0.0 141 0.20    141 0.0 0.00    0.0 0.003   0.000   23.9    39  9.1 23.4    0.00    24  1   100.0   1   1.903537153899393   652.4695341279602

2015-08-01 07:05    0.25    0.52    0.00    0.52    0   14.8    14.8    14.7    67  8.7 0.0 --- 0.00    0.0 --- 14.8    14.3    14.3    16.3    1016.3  0.00    0.0 148 0.21    148 0.0 0.00    0.0 0.002   0.000   23.9    39  9.1 23.4    0.00    23  1   100.0   1   1.897596925383499   654.5120216976508
 ........
 ........

i want to plot the 43rd row in relation to the 3rd and 25th row :-) So those are the rows want to pick out of the file:

0.23 156 660.7143449269239
0.25 153 660.7143449269239
0.25 139 654.4985251906015
0.26 139 652.0519661851259

I want to set the 660.7143449269239 in relation to the 0.23 and 156 and plot a 2d contour plot .

I read the documentation but I don't know if those rows are sufficient for a Contour Plot or if I need to alter them and if so, can I do this in gnuplot or do I have to rewrite the file tiself?

does my data need to look like:

0.23 156 660.7143449269239(0.23,156)
0.25 153 660.7143449269239(0.25,253)

vagoberto · Accepted Answer · 2015-10-07 20:16:30Z

1

This is the way to go (comments through the code):

set dgrid3d        # enable 3D data read from a scattered data set in file
set contour base   # enable contour drawing 
set view map       # if you want to see the graph from above (2D plot)
unset surface      # do not plot the surface, only the contour

# finally, plot your data selecting columns 3, 25, and 43
splot 'datafile' using 3:25:43

answered Oct 7, 2015 at 20:16

vagoberto

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2 Comments

Peter S Over a year ago

okay thanks, so I end up with rounded z values for the Contour Plot is that correct? That s what dgrid3d does?

vagoberto Over a year ago

Yes. Since your data seems to be scattered (it seems to be measurements of an experiment or other event), it is necessary to use dgrid3d in order to compute the contours. dgrid3d interpolates (through averages or splines) the z values into an uniform grid in the xy-plane. Then the interpolated points is plotted instead of the original data. You can control the way dgrid3d interpolates/averages the data (type help dgrid3d in gnuplot). If your data is already uniformly distributed, it is not necessary to use dgrid3d.

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