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Chad Greene
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Seeking a fast way to determine if axes are current

Asked by Chad Greene
on 29 Sep 2014
Latest activity Edited by Cam Salzberger on 14 Sep 2017
I've written a function that includes a line to determine if axes are current. This is the line:
AxesAreCurrent = ~isempty(findobj(gcf,'type','axes'));
From the profiler I see that about three quarters of the processing time of my 400 line function is taken up by this line. It's only a fraction of a second, but I will be calling this function thousands of times in a row, and I'd like to speed it up. Is there a faster check to determine if any axes are current?

  5 Comments

Hi Joseph and José-Luis. My function plots some surfaces. But before plotting these surfaces, I'd like to determine if a plot is already open. If a plot is not already open, my function plots the surfaces then sets lighting, sets axis limits, sets view angle, etc. On the other hand, if when the function is called, a figure is already open and axes are current, my function adds the new surfaces to the plot without attempting to set lighting or axis limits.
The intent is to let the function figure out, without user input, if initial formatting needs to be applied.
Tricky...especially since gca will create axes if they don't exist.

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3 Answers

Answer by José-Luis
on 29 Sep 2014
Edited by José-Luis
on 29 Sep 2014
 Accepted Answer

isempty(get(gcf,'CurrentAxes'))
will tell you if there are any current axes in gcf . This is basically an edit of the gca() function that does not create new axes if none exist.

  2 Comments

Nice! Takes about 1/3 of the time of my original findobj method. Thanks José-Luis.
My pleasure.

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Answer by Alexander Laut on 14 Sep 2017

i don't know how this compares but i found this solution useful for my needs to check if an axis exists without creating a figure so i can reset the color order
%%ResSet Color Order
if ~isempty(findobj(allchild(0),'Type','axes'))
set(gca(),'ColorOrderIndex',1) % resets color order if an axis exists
end

  1 Comment

There are a couple of issues with this piece of code. I assume you're trying to find even figures with hidden figure handles, which is why you used allchild. However, if the axes also has a hidden figure handle, then findobj won't find it, though findall would. If the axes handle is visible, but the figure handle is not, then gca will create a new figure and axes. For example:
f = figure('HandleVisibility','off');
a = axes('HandleVisibility','on','Parent',f);
if ~isempty(findobj(allchild(groot),'Type','axes'))
set(gca,'ColorOrderIndex',1)
end
If you want to deal with hidden handles, I'd suggest something more akin to this:
hAxes = findall(groot,'Type','axes')
if ~isempty(hAxes)
set(hAxes(1),'ColorOrderIndex',1)
% Or even set(hAxes, ...) to change all properties of all axes
end
It's not as clean, since there's no guarantee that hAxes(1) is the most recently clicked axes. However, a hidden handle figure/axes will never be in the 'CurrentFigure' or 'CurrentAxes' property, so that is kind of moot. I'll post something that can handle this in a separate answer.
-Cam

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Answer by Cam Salzberger on 14 Sep 2017
Edited by Cam Salzberger on 14 Sep 2017

As Alexander pointed out, it may be desirable to avoid creating a figure with gcf. However, gca will have the same issues, if there are hidden handles. Here's something that can handle all hidden handle situations:
I'd suggest first checking for visible figures and axes without creating them, before then checking for hidden ones:
hFig = get(groot,'CurrentFigure');
if ~isempty(hFig)
hAx = get(hFig,'CurrentAxes');
if isempty(hAx)
hAxes = findall(hFig,'Type','axes');
hAx = hAxes(1);
end
else
hFigures = findall(groot,'Type','figure');
hAx = gobjects(0,0);
if ~isempty(hFigures)
k = 1;
while k < numel(hFigures) && isempty(hAx)
hAxes = findall(hFigures(k),'Type','axes');
if ~isempty(hAxes)
hAx = hAxes(1);
end
k = k+1;
end
end
end
You know, just to be really thorough. Now hFig and hAx will be a figure or axes handle respectively, or empty if there isn't one.
Qualifier: This is largely untested code, but hopefully can give you a guideline to work from.
-Cam

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