Behavior of subplot

[John W. Eaton]

On  9-Feb-2009, Michael D. Godfrey wrote:

| I used an old function that contained subplot calls
| with the current development Octave.  It took a while
| to recover the old behavior.  The example below shows
| what seems to me counter intuitive behavior:
| 
| hold off
| x = [0:.1:10];
| sx = sin(x);
| cx = cos(x);
| for k=1:3
| axis([1,10,-1,1]);
| subplot(2,3,k);
| plot(x, sx);
| axis([1,20,-1,1]);
| subplot(2,3,3+k);
| plot(x, 10*sx);
| endfor;
| 
| ====================================
| For me the resulting six plots have the following properties:
| 
| Plots 1, 2, 3 (top row)  xscale: 1:20, yscale: -1:+1
| Plots 4 and 5:               xscale:1:10, yscale: -1:+1
| Plot 6:                            xscale: 0:10; yscale: -10:+10
| ======================================
| 
| For me, predictable results could only be obtained by using
| the sequence:
| 
| subplot()
| hold on
| axis()
| plot()
| 
| Also, I noticed that the behavior if the commands were entered
| at the Octave prompt is different from the result of executing
| them from a script.  What happens is that subsequent subplot
| commands "overwrite" the displayed result of a previous command.

In the old days, Octave followed the gnuplot way of doing plotting, so
that a call to axis (for example) affected subsequent plots.  But now
we are doing things in the Matlab way, so calls to axis affect the
current plot.  So I suspect you just need to move the axis commands
afte the plot commands, like this:

  hold off
  x = [0:.1:10];
  sx = sin(x);
  cx = cos(x);
  for k=1:3
    subplot(2,3,k);
    plot(x, sx);
    axis([1,10,-1,1]);
    subplot(2,3,3+k);
    plot(x, 10*sx);
    axis([1,20,-1,1]);
  endfor

Except for possible spacing problems, does that produce the plot you
expect?

jwe