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update 2004/9/15
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About 3-Dimensional Plot (No.2)

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How do I draw a 3-dim. grid graph from 3-Dim scattered data

Suppose your data to be plotted are 3-dimensinonal scattered data (x,y,z) with arbitrary order. With the splot command, gnuplot generates points or lines in a 3-dim. space. 

# X          Y         Z
9.862e-01 -8.062e-02   0.001
9.786e-01 -1.134e-01   0.002
9.720e-01 -1.382e-01   0.003
.....
-1.849e-01 -2.165e-01  80.000
-2.412e-01 -1.301e-01  90.000
-2.611e-01 -4.825e-02 100.000

gnuplot> set xrange [-1:1]
gnuplot> set yrange [-1:1]
gnuplot> set ticslevel 0
gnuplot> splot "datafile.dat" u 1:2:3 with lines
fig/sample6.6a

In order to generate a 3-dim. grid graph from those data, use set dgrid3d. Height of each mesh is determined automatically by a weighted average of the data inside the grid. The number of mesh in the X- and Y-directions can be specified by set dgrid3d x-mesh, y-mash.

gnuplot> set dgrid3d 30,30
gnuplot> set hidden3d
gnuplot> splot "datafile.dat" u 1:2:3 with lines
fig/sample6.6b
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