How to detect if a figure exist?

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.

Answer 1

[Brendan Hamm]

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

[John]

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]

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?

Answer 2

[Stephen23]

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)

[Stanislav Ginzburg]

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]

"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.