Question

Is there a way to know how many figures are opened in matlab?

Answer 1

Use:

numel(get(0,'Children'));

You can also use what @triazotan suggested, using the findobj function. However it will be slower, because you need to go through all of your objects.

Edit:
I’ve decided to see how findobj works exactly. It is a much more complicated way of going through all of the objects in get(0,’Children’)
Here is small digest from the file that is being called from findobj:
Check out the builtin( ‘get’, 0, ‘ShowHiddenHandles’ ) which is essentially a get(0,’Children’) in the middle:

function h = findobjhelper( varargin )

%Copyright 2009-2010 The MathWorks, Inc.

allowHVHandles = true;

nin = nargin;
rootHandleVis = builtin( 'get', 0, 'ShowHiddenHandles' );

% See if 'flat' keyword is present 
hasflat = false;
if (nin > 1) 
    if strcmp( varargin{2}, 'flat' ) % Does the 'flat' keyword exist
        hasflat = true;
    end
end

if nin == 0
    if feature('HgUsingMatlabClasses')
        h = findobjinternal( 0, '-function', @findobjfilter );  
    else
        h = findobjinternal(0);
    end

Thus, using findobj is clearly an overkill.