How to save figures in a for loop?

I've created a for loop for 5 subjects. The first times the loop runs, I get a plot for subject one. I want to save this figure under the name 'plot_subject_1'. The next time the loop runs, I want to save the figure under the name 'plot_subject_2'. How do I do this?

Answer 1

[Image Analyst]

This is well covered by the first set of well-commented code in the FAQ: http://matlab.wikia.com/wiki/FAQ#How_can_I_process_a_sequence_of_files.3F I'm sure you'll have no trouble using sprintf() and fullfile() to create your filenames after you see the FAQ. Let us know if you can't get it to work.

Inside the loop, use export_fig() to save the figures or axes as PNG images (or other formats). http://blogs.mathworks.com/pick/2010/05/28/creating-and-exporting-publication-quality-graphics/

[Sam]

I have never used sprintf or any other command like that. I'm very new to Matlab. I know that these commands are used for making your own filesnames, etc. But I can't seem to understand how to store it in a datafile. Well, it's a bit chaos for me... I'm sorry

[Image Analyst]

Try this:

folder = 'c:/whatever';
for k = 1 : 5
  % Change your figure somehow....I don't know what you're doing here.
  
  % Create a PNG filename.
  pngFileName = sprintf('plot_subject_%d.png', k);
  fullFileName = fullfile(folder, pngFileName);
    
  % Then save it
  export_fig(fullFileName);
end

[Sam]

It works when I do: saveas(gcf, fullFileName). Another question: is there a reason why to use %d?

[Image Analyst]

Yes. If you don't use %d then the number will not be inserted into the filename string. That tells sprintf to insert the number there as an integer.

If that answers all your questions, can you mark the ANswer as Accepted and/or Vote for it? Thanks.

[Jakub Jurasz]

@Image Analyst It has been long time since you have posted this.

I am following your answers and I find them super helpful.

Any ideas how to speed up saving the figures in a loop when a lot of figures is about to be saved? PNG are relatively small but after saving 400 of them Matlab is already using over 1GB of ram.

for i=1:8760;
    figure()
    % code for making the figure - quite long,  a mix of surfplot + countour 
    saveas(gcf,sprintf('Fig_%d.png',i));
    clf
end

I am thinking about doing it in batches but I guess there must be a way to do it faster.

Any help would be much appreicated!

[Image Analyst]

Try moving figure outside the for loop. There is probably no need to create a new figure each iteration. Also make sure hold is not on when you display the image and you might do a "cla reset" before each call to imshow()

hfig = figure;
for k = 1 : 8760
    fileName = whatever...
    cla reset;
    % code for making the figure - quite long,  a mix of surfplot + countour 
    exportgraphics(gcf, sprintf('Fig_%d.png', k)); % Or gca instead of gcf.
    % exportgraphics() available in R2020a or later.
    clf
end

Answer 2

[nikhil baraiya]

Its Working Fine Thanks