Re: Line plotting not working in an Octave 3.8.1 script

[Mike Miller]

On Thu, Jun 12, 2014 at 08:30:16 -0700, fbarbuto wrote:
> Here it is:
>
> http://trash.ctdo.de/a/586hekjm938

You are misunderstanding how the plot function operates, and perhaps
more fundamentally the way that operators and functions work with
vectors.

Your script does not plot a line, it plots a series of points on the
same axis. Here is the relevant part of your script inline:

> for x=1:5
>     arg = x/20.0
>     t = Talbot(arg, 32)
>     plot(arg,t,'bd',arg, sqrt(arg)*besselj(1, 2.0*sqrt(2.0*arg)),'r-');
>     hold on;
> endfor

This loop does not create a line connecting each of the pairs of
points you are passing to the plot function. If you pass two pairs of
vectors to plot, it will plot a line. If you pass only scalars it will
plot a point.

Instead of looping over the points, you want to collect all values
into vectors to pass to a single call to plot to get a line.

Better still would be if your Talbot function operated on arg as a
vector argument. The besselj function already does. For example try
this:

  arg = [1:5]/20;
  plot (arg, sqrt (arg) .* besselj (1, 2 * sqrt (2 * arg)), "r-");

-- 
mike