How to detect if a figure exist?

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John 2016-1-14

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https://ww2.mathworks.cn/matlabcentral/answers/263788-how-to-detect-if-a-figure-exist

评论： Stephen23 2022-11-13

采纳的回答： Brendan Hamm

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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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Answer 1

Brendan Hamm 2016-1-14

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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

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John 2016-1-14

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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 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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Answer 2

Stephen23 2016-1-14

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编辑：Stephen23 2016-1-14

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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)

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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 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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