How to detect if a figure exist?

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John
John 2016-1-14
评论： Stephen23 2022-11-13
To save the figure if one exists with:
saveas(gcf,figname);
the problem is that if no figure exists, it'll create a figure. How to detect if a figure exist before using above saveas command to avoid the creation of an empty figure?
Thanks.

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采纳的回答

Brendan Hamm
Brendan Hamm 2016-1-14
In 2014b and later you can query whether the Graphics Root objects has any children:
g = groot;
isempty(g.Children) % True if there are no open graphics objects, false otherwise
  2 个评论
John
John 2016-1-14
Thanks, I did this and it worked as well:
fig = get(groot,'CurrentFigure');
if ~isempty(fig)
filename=strcat(fname,'_',str,'.fig');
saveas(gcf,filename);
end
Roger Breton
Roger Breton 2022-2-8
Thank you for sharing this tidbit of code!
It worked perfect for me in my script.
But I could not find "CurrentFigure' in the list of properties when I issued get(fig) from the command window in debuig mode?

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Stephen23
Stephen23 2016-1-14
编辑：Stephen23 2016-1-14
The most reliable solution is to move your programming up a notch: use explicit handles and keep track of them.
While gcf and gca are fine for the command-line and playing with scripts, when you want to write more advanced functions then:
  • do not use gcf, gca.
  • store the handle of every axes, figure, and other relevant objects.
  • explicitly specify the parent of every object when it is created, plotted, etc.
When you code properly then your quest is trivial using ishghandle:
ishghandle(stored_handle)
  2 个评论
Stanislav Ginzburg
Stanislav Ginzburg 2022-11-13
Sometimes you may get handle on empty object plot([1,2], [NaN, NaN]); Result of ishghandle is true, Groot return handler of figure. And not empty too. The good practice is to prevent save empty objects.
Stephen23
Stephen23 2022-11-13
"The good practice is to prevent save empty objects."
No, empty plots may also be information: it may be a perfectly valid and important result that for some figure nothing is plotted. This depends entirely on the specific situation and thus is the responsibility of the user to check.

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