[Gnuplot-info] Plotting points on a grid

[Martin <ap...@ds...>]

Hello

I have an instruction set for graph generation like this:

set title "" 0, 0, 0 font "arial, 12"
show title
set xlabel "Accelera" font "arial, 10"
set ylabel "Accelera" font "arial, 10"
set zlabel "null" offset 4 font "arial, 10"
set xrange [6:50]
set yrange [40:90]
set zrange [1:36]
set dgrid3d 30, 30, 3
set view 60, 30, 1, 1
set grid x y z
set border
set key
splot "data.txt" using 2:3:4 with lines notitle, "data.txt" using 2:3:4:1 with 
labels notitle
set contour surface
set output "graph.png"
set term png size 1024, 768
replot
set terminal win
reset

This uses data.txt as follows:

+ 6.6 59 1.3
+ 6.6 59 1.3
+ 6.6 59 1.3
+ 7.3 65 4.2
+ 7.3 65 3.7
+ 7.3 65 4.4
+ 50 45 35.6
+ 50 45 32.4
+ 50 45 31
+ 10 90 15.5
+ 10 90 15.8
+ 10 90 16.8

But my concern is the splot action: when the graph is generated, plot points 
are shown off the grid or pm3d (if used) surface created and I don't know why. 

Is it to do with the computation of the lines within splot?

Any help with this would be much appreciated.

Many thanks

Martin O'Shea.