By: Naor

Naor — Thu, 15 Oct 2009 22:41:00 +0000

very strange indeed.

By: Benoit

Benoit — Thu, 15 Oct 2009 09:54:43 +0000

In this case, lines are faster than scatter only when colors are used and different for each point (???). Observe this script:

%% Scatter creation
T = 0;
cla
for i=1:10
	x = rand(1,1000);
	y = rand(1,1000);
	cla
	t = cputime;
	h = scatter( x,y );
	drawnow
	T = T + (cputime-t);
end
fprintf( 'Scatter creations: %.2f\n', T )
 
%% Lines creation
T = 0;
cla
for i=1:10
	x = rand(1,1000);
	y = rand(1,1000);
	cla
	t = cputime;
	h = line( [x;x], [y;y], props{:} );
	drawnow
	T = T + (cputime-t);
end
fprintf( 'Line creations: %.2f\n', T )
 
%% Scatter modification
T = 0;
cla
x = rand(1,1000);
y = rand(1,1000);
h = scatter(x,y);
for i=1:10
	y = rand(1,1000);
	t = cputime;
	set( h, 'YData', y );
	drawnow
	T = T + (cputime-t);
end
fprintf( '\nScatter modifications: %.2f\n', T )
 
%% Lines modification
T = 0;
cla
x = rand(1,1000);
y = rand(1,1000);
h = line( [x;x], [y;y], props{:} );
for i=1:10
	y = rand(1,1000);
	t = cputime;
	set( h, {'YData'}, num2cell([y;y]',2) );
	drawnow
	T = T + (cputime-t);
end
fprintf( 'Line modifications: %.2f\n', T )
 
%% Scatter color creation
T = 0;
cla
for i=1:10
	x = rand(1,1000);
	y = rand(1,1000);
	c = rand(1000,3);
	cla
	t = cputime;
	h = scatter( x,y,50,c );
	drawnow
	T = T + (cputime-t);
end
fprintf( '\nScatter color creation: %.2f\n', T )
 
%% Lines color creation
T = 0;
cla
for i=1:10
	x = rand(1,1000);
	y = rand(1,1000);
	c = rand(1000,3);
	cla
	t = cputime;
	h = line( [x;x], [y;y], props{:} );
	set( h, {'MarkerEdgeColor'}, num2cell(c,2) );
	drawnow
	T = T + (cputime-t);
end
fprintf( 'Line color creation: %.2f\n', T )
 
%% Scatter color modification
T = 0;
cla
x = rand(1,1000);
y = rand(1,1000);
c = rand(1000,3);
h = scatter(x,y,50,c);
for i=1:10
	y = rand(1,1000);
	t = cputime;
	set( h, 'YData', y );
	drawnow
	T = T + (cputime-t);
end
fprintf( '\nScatter color modification: %.2f\n', T )
 
%% Lines modification
T = 0;
cla
x = rand(1,1000);
y = rand(1,1000);
c = rand(1000,3);
h = line( [x;x], [y;y], props{:} );
set( h, {'MarkerEdgeColor'}, num2cell(c,2) );
for i=1:10
	y = rand(1,1000);
	t = cputime;
	set( h, {'YData'}, num2cell([y;y]',2) );
	drawnow
	T = T + (cputime-t);
end
fprintf( 'Line color modification: %.2f\n', T )

When you execute this script, you obtain:

Scatter creations: 0.76
Line creations: 9.53
 
Scatter modifications: 0.61
Line modifications: 1.51
 
Scatter color creation: 4.02
Line color creation: 17.07
 
Scatter color modification: 4.34
Line color modification: 1.53

Magic, isn’t it?
Sometimes, I wonder if Matlab was not developed at Hogwarts…

By: Naor

Naor — Wed, 14 Oct 2009 20:05:57 +0000

Now this is really interesting. Now I’m curious about generating 1000 line objects with one data point/marker each, and saving into a handle vector? Is this what scatter is doing under the hood?

Comments on: Performance: scatter vs. line

By: Naor

By: Benoit

By: Naor