MATLAB Central Newsreader - Working with large data sets

Working with large data sets

David Doria — Wed, 27 Aug 2008 23:16:02 -0400

I have 20,000 3D points that I would like to plot. Matlab
just grinds and grinds and eventually the system freezes or
I get a "cache memory exhausted" error. Is there a good way
to do something like this with matlab?

Thanks,

David

Re: Working with large data sets

Paul — Thu, 28 Aug 2008 01:38:02 -0400

"David Doria" <daviddoria@gmail.com> wrote in message
<g94n7i$haa$1@fred.mathworks.com>...
> I have 20,000 3D points that I would like to plot. Matlab
> just grinds and grinds and eventually the system freezes or
> I get a "cache memory exhausted" error. Is there a good way
> to do something like this with matlab?
>
> Thanks,
>
> David

20,000 point is 'only' approximately 140x140 matrix and
Matlab should handle this (in plots) with ease. Are you
just trying to plot or are you actually trying some
calculations when you say grinds and grinds?

Re: Working with large data sets

David Doria — Thu, 28 Aug 2008 12:30:05 -0400

> 20,000 point is 'only' approximately 140x140 matrix and
> Matlab should handle this (in plots) with ease. Are you
> just trying to plot or are you actually trying some
> calculations when you say grinds and grinds?

it's a 20,000 x 3 matrix, isn't it? Maybe the problem was
that I was connecting the points (aka drawing triangles).
I'll try this morning to plot just the points and see if it
does any better.

David

Re: Working with large data sets

David Doria — Thu, 28 Aug 2008 13:22:02 -0400

Yea, even when I just plot the points, it is very very slow
(ie non-smooth rotation, etc). I have a dual core 3ghz
machine with 4gb of ram so that isn't the problem...

Re: Working with large data sets

Bill August — Thu, 28 Aug 2008 14:07:43 -0400

> Yea, even when I just plot the points, it is very
> very slow
> (ie non-smooth rotation, etc). I have a dual core
> 3ghz
> machine with 4gb of ram so that isn't the problem...
Hi
The speed is also related to how many handles you are using. So the question is how do you plot the points?
Are you using plot3d or line which show the uniformed points (only one handle). Or you plot them one by one (20000 handles) with differnet state?
Regards.

Re: Working with large data sets

David Doria — Thu, 28 Aug 2008 14:21:02 -0400

> Hi
> The speed is also related to how many handles you are
using. So the question is how do you plot the points?
> Are you using plot3d or line which show the uniformed
points (only one handle). Or you plot them one by one (20000
handles) with differnet state?
> Regards.

Ah great! I was plotting them individually, when I switched
to plotting the whole matrix at the same time it worked MUCH
better.

ie.

for i = 1:size(V,1)
plot3(h, V(i,1), V(i,2), V(i,3), 'o');
end

VS

plot3(h, V(:,1), V(:,2), V(:,3), 'o');

Thanks!