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## 2D sampling (u and v axes)

Computed functions or data generated for the pseudo-file '++' use samples generated along the u and v axes. See special-filenames ++. 2D sampling can be used in either plot or splot commands.

Example of 2D sampling in a 2D plot command. These commands generated the plot shown for plotstyle with vectors. See vectors.

         set urange [ -2.0 : 2.0 ]
         set vrange [ -2.0 : 2.0 ]
         plot '++' using ($1):($2):($2*0.4):(-$1*0.4) with vectors

Example of 2D sampling in a 3D splot command. These commands are similar to the ones used in sampling.dem. Note that the two surfaces are sampled over u and v ranges smaller than the full x and y ranges of the resulting plot.

         set title "3D sampling range distinct from plot x/y range"
         set xrange [1:100]
         set yrange [1:100]
         splot sample [u=30:70][v=0:50] '++' using 1:2:(u*v) lt 3, \
               [u=40:80][v=30:60] '++' using (u):(v):(u*sqrt(v)) lt 4

The range specifiers for sampling on u and v can include an explicit sampling interval to control the number and spacing of samples:

         splot sample [u=30:70:1][v=0:50:5] '++' using 1:2:(func($1,$2))