Re: help offer

[Daniel J Sebald]

David Grohmann wrote:

> There is this but my guess is most of it is out of date as well.
>
> http://wiki.octave.org/wiki.pl?MostWanted

On the matter of this item:

o A means of passing data to gnuplot that allows binary data to be transferred 
and does not involve writing temporary files. This is particularly evident if 
you try plotting a large vector (100000 points or more) and compare the speed 
difference between Octave and Matlab.

I've put together a simple test that uses "fwrite" rather than "fprintf".  
Using:

x = rand(1,100000);

the following:

tic; plot(x)
toc

takes:

9.4 s with ASCII fprintf() version
4.9 s with binary fwrite() version

When I isolate tic/toc around the fprintf and fwrite commands in 
__go_draw_axes__.m, I see:

12.1 s with ASCII fprintf() version
2.9 s with binary fwrite() version

Now, one big question is why the time *increases* when I parred down the tic/toc 
to a single script command?  Perhaps there is some interaction with the 
tic/toc/fprintf; I'm not sure.

Another interesting detail is that:

A = rand(1000,100);

tic; image(A)
toc

takes 1.7 s.  (It's binary transfer.)  Which tells me that a lot more work goes 
on inside gnuplot/gnuplot_x11 when plotting 100,000 lines than there is when 
plotting a single image.

Dan