Re: Changing the Z axis as displayed in splot

Hello Nicolas

In your instance, does it help if you switch the definition of the upper /
lower level of corresponding axis?

Your post does not provide (synthetic / anonymized) data to work with, nor the
script deployed.  This is the reason why I departed from one examples about the
sync(u,v) functions of the [demo page] (with the [complete script]).  Line 25
reading

```
set zrange [ -0.500000 : 1.00000 ] noreverse writeback
```

was replaced by

```
set zrange [ 1.0 : -0.5 ] noreverse writeback
```

To generate a permanent record (gnuplot 6.0 patchlevel 3 as packaged for Linux
Debian 14/forky), the first two lines of the script were decommented, too.  By
this, the cone now is a deep depression, the direction of the vertical axis is
inverted:

```
set terminal pngcairo  transparent enhanced font "arial,10" fontscale 1.0 size
600, 400 
set output 'surface1.16.png'
set dummy u, v
set label 1 "This is equal to 1" at -5.00000, -2.00000, 1.50000 center
norotate back nopoint
set arrow 1 from -5.00000, -2.10000, 1.40000 to 0.00000, 0.00000, 1.00000 head
back nofilled linewidth 1.000 dashtype solid
set view 70, 20, 1, 1
set samples 51, 51
set isosamples 21, 21
set style data lines
set ztics  norangelimit -1.00000,0.25 ,1.00000
set title "Sinc function" 
set trange [ * : * ] noreverse nowriteback
set urange [ * : * ] noreverse nowriteback
set vrange [ * : * ] noreverse nowriteback
set xlabel "X axis" 
set xlabel  offset character -3, -2, 0 font "" textcolor lt -1 norotate
set xrange [ -1.00000 : 1.00000 ] noreverse nowriteback
set x2range [ * : * ] noreverse writeback
set ylabel "Y axis" 
set ylabel  offset character 3, -2, 0 font "" textcolor lt -1 rotate
set yrange [ -1.00000 : 1.00000 ] noreverse nowriteback
set y2range [ * : * ] noreverse writeback
set zlabel "Z axis" 
set zlabel  offset character -5, 0, 0 font "" textcolor lt -1 norotate
# set zrange [ -0.500000 : 1.00000 ] noreverse writeback
set zrange [ 1.0 : -0.5 ] noreverse writeback  # line edited
set cbrange [ * : * ] noreverse writeback
set rrange [ * : * ] noreverse writeback
set colorbox vertical origin screen 0.9, 0.2 size screen 0.05, 0.6 front
noinvert bdefault
sinc(u,v) = sin(sqrt(u**2+v**2)) / sqrt(u**2+v**2)
VERSION = "gnuplot version 6.0.3"
NO_ANIMATION = 1
## Last datafile plotted: "$grid"
splot [-12:12.01] [-12:12.01] sinc(u,v)
```

Best regards,
Norwid

[demo page]: https://gnuplot.sourceforge.net/demo_6.0/surface1.html
[complete script]: https://gnuplot.sourceforge.net/demo_6.0/surface1.16.gnu


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