RE: Plotting basics

[Damian Harty]

>  Is it a problem to plot zeros? I'm not specifying any axis bounds, so maybe 
> the auto-bounds generator is specifying zero,
> and that conflicts with the semilogy() function? I need to show zeros, but 
> there needs to be logarithmic scaling too.

Yes, the log of zero is undefined. You might like to add a "small" number to 
your array that disappears off the left hand end of your graph.

> I get errors about "subscript indices must either be positive integers less 
> than 2^31..." What does it mean? Why can't I have a linear plot?

You are trying to plot an array element that is beyond the bounds of what is 
possible. Since I find it unlikely you have an array with 2147483648 elements, 
I wonder if it is possible that you aren't doing what you *think* you are 
doing. This is a remarkably common state of affairs.

> When I use the axis() function, all my inputs are ignored. It just plots the 
> same auto-bounds that it was plotting before.
> I call it like "axis([1,30,-100,1000]);" before anything else happens in the 
> script.

This code works for me:

  time=0:0.1:10;
  sine=sin(time*2*pi/5);
  figure
  plot(time,sine)
  axis([-1,11,-1.5,1.5])

Try putting your axis command at the end.

Damian
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