Avoid Repeated Searches for Objects

When you search for handles, MATLAB^® must search the object hierarchy to find matching handles, which is time-consuming. Saving handles that you need to access later is a faster approach. Array indexing is generally faster than using findobj or findall.

This code creates 500 line objects and then calls findobj in a loop.

figure
ax = axes;
for ix=1:500
   line(rand(1,5),rand(1,5),'Tag',num2str(ix),'Parent',ax);
end
drawnow;
for ix=1:500
   h = findobj(ax,'Tag',num2str(ix));
   set(h,'Color',rand(1,3));
end
drawnow;

A better approach is to save the handles in an array and index into the array in the second for loop.

figure
ax = axes;
h = gobjects(1,500);
for ix = 1:500
   h(ix) = line(rand(1,5),rand(1,5),'Tag',num2str(ix),'Parent',ax);
end
drawnow;
% Index into handle array
for ix=1:500
   set(h(ix),'Color',rand(1,3));
end
drawnow

Limit Scope of Search

If searching for handles is necessary, limit the number of objects to be searched by specifying a starting point in the object tree. For example, specify the starting point as the figure or axes containing the objects for which you are searching.

Another way to limit the time expended searching for objects is to restrict the depth of the search. For example, calling findobj with the 'flat' option restricts the search to the objects in a specific handle array.

Use the findobj and findall functions to search for handles.

For more information, see Find Objects