scatter too slow

Hi, I want to plot particles according to their longitudes, and latitudes and to plot them according to their times (date of birth). That's why I used scatter(lon, lat, 4, time); It works very well for small numbers (10, 20,30,80), but When I use it with bigger numbers (I tried 9 000, and I need in reality 100 000), it's a crash, and I have to stop the process each time.

Does any body have a solution?

Answer 1

[Sean de Wolski]

Are you sure a 2-dimensional histogram viewed as a mesh or surf wouldn't better suit your needs? I have a lot of trouble believing that you'll be able to depict anything but a blob with 100000 points on most (all) monitors.

If you use a 2-dimensional histogram you'll be able to see how many points are in an area specificed by the size you need. I think this will be much more useful as a visualization/analysis tool.

If this is what you want, look at Bruno's: FEX:histcn

Answer 2

[the cyclist]

This code executes successfully in about 30 seconds on my machine.

n = 100000;

x = rand(n,1);
y = rand(n,1);
c = rand(n,3);

tic
scatter(x,y,25,c);
toc

Are you embedding any calculations inside your plotting? For example, datenum() can take a notoriously long time to calculate.

Answer 3

[Mariem]

When I write the same code as you, I have to stop the process, because noting happens:

>>> n = 100000;

x = rand(n,1); y = rand(n,1); c = rand(n,3); tic scatter(x,y,25,c);

toc

>>>

>>>Elapsed time is 514.298 seconds.

[Walter Roberson]

Which renderer are you using? get(gcf,'Renderer')

If it is OpenGL, then please use the command

opengl info

and look at the 'Software' line of the output. "false" corresponds to "opengl hardware" and "true" corresponds to "opengl hardware" (which would normally be faster.)

[Sean de Wolski]

You're trying to draw 100000pts. Do you really think you'll be able to distinguish between them if they ever do draw?

[Mariem]

yes, because after that, I will plot the particles according to the month, it's easy to do. My problem now is just how to display scatter.

Answer 4

[Mariem]

get(gcf,'Renderer')

>> painters

so I made >> set(gcf, 'Renderer', 'opengl')

>> set(0,'DefaultFigureRenderer','opengl')

but when I try opengl info or bench, octave doesn't recognize my command.

>>>error: `opengl' undefined near line 36 column 1.

[Walter Roberson]

Octave... not many of us here have the experience to talk about what works well or does not work in octave.

Answer 5

[per isakson]

See: better way to visualize profile data

In the file exchange there are some contributions, which implement the approach I propose. E.g "plotc" and "Dot plot rather than scatter plot". There are more, but I cannot remember the names.

Answer 6

[Mariem]

I tried them, but I couldn't adapt them to my program, I am still a novice in octave.