Re: [Gnuplot-info] keep ratio for all axis, axis in same place

[Lars H. <la...@ho...>]

Hi!

> a) I am using splot command to paint some figures. I
> would like that gnuplot autoscale (ok, done by default)
> but I would like that gnuplot keeps the ratio for all
> axis. Example: if gnuplot decides that x-axis has to be
> from -6 to -6, I want that y-axis is from -6 to 6 and
> z-axis too. Else my figures gets with "rare" shapes

The simpest way to do this would of course be to choose the 
ranges by hand. You may use a variable within the set 
[xyz]range-command. Maybe your mathematical equations or 
yoour data allows to calcutlate good borders.

As far as I could find out by studying the documentation, 
there is no way of telling gnuplot to keep an aspect ratio 
in 3D-plots. I had a kind of "brute force"-idea that might 
work, but I've not tested it yet. Let's say your x-range is 
choosen quite qell. So your aim is to set the y- and z-axis 
to the same ranges. I would first set the terminal to 
unkown, so that no output is created. Then I would do a 
coordinate transformation that changes x with y (resp x 
with z). If I would now plot the graph, the y-axis (z-axis) 
should have the right range. Before that I use the 
mechanism of writing back the automatically calulated 
ranges:
  set yrange [] writeback
By doing this, gnuplot writes the now well calculated values 
for the upper and lower border of y to a memory. Afterwards 
I would reset the terminal to the one I would like to use 
for my output. If you now use 
  set yrange [] nowriteback
gnuplot should (If I am right) not change the ranges for y.


> b) I want that x-axis, z-axis and y-axis are always
> represented in z=0, x=0 and y=0. Any way to do it? z-axis
> sometimes is represented in -6, is a bit confusing :-)

Your problem cant't be solved completely, since gnuplot does 
not allow to move the z-markers from the border to the 
axes. The nearest solution would be like follows

  set ticslevel 0   # puts z=0 to x=0,y=0
  set zeroaxis linetype 1 # produces lines on the axes x,y
  unset border # switches off the frame around the plot
  set xtics axis nomirror
  set ytics axis nomirror # puts the tics to the axes x,y

You may "simulate" an z-axis by using the set arrow command, 
but you can't move the z-tics to this line. 


HTH
Lars