How to save a plot as a file, after each iteration off a for loop.

I was wondering if it's possible to save a plot after each iteration of a for loop, and adda Date, Latitude and Longtitude to the title?

Here is the script I'm working on(the variables are added from a 5 column cell array(newdata)):

D = newdata(:,2);%depth
S = newdata(:,1); %salinity
t1 = cell2mat(newdata(:,3)); %days since 1950-01-01
t2 = 19500101;
t3 = datetime(t2,'ConvertFrom','yyyymmdd');
t4 = juliandate(t3);
t5 = t1 + t4;
T = datetime(t5,'convertfrom','juliandate'); %datenumtime
Lat = newdata(:,4);
Long = newdata(:,5);

[L,W] = size(newdata);
for i = 1 : L
    x = S{i,1};
    y = D{i,1};
plot(x,y),hold on
scatter(x,y),hold off
legend
xlabel('Salinity')
ylabel('depth [m]')
end

Would appreciate som help.

Answer 1

[Ameer Hamza]

See exportgraphics(): https://www.mathworks.com/help/matlab/ref/exportgraphics.html. You can call it inside the for loop to save the figures

for i = 1 : L
    x = S{i,1};
    y = D{i,1};
    plot(x,y),hold on
    scatter(x,y),hold off
    legend
    xlabel('Salinity')
    ylabel('depth [m]')
    title(sprintf('Date:%s Lat:%d  Lon:%d', string(t5(i)), Lat(i), Long(i)));
    exportgraphics(gca, ['file' num2str(i) '.png'])
end

[johndoe]

Great thanks! :)

[Ameer Hamza]

Glad to be of help.

[johndoe]

When I use:

exportgraphics(gca, ['file' num2str(i)] '.png')

i get this error:

Error: File: Skript_haloklin_plots.m Line: 23 Column: 41
Invalid expression. Check for missing multiplication operator, missing or unbalanced delimiters, or other syntax
error. To construct matrices, use brackets instead of parentheses.

Do you know what could be the cause of that?

[Ameer Hamza]

What is the value of variable 'i' when you run this line?

[johndoe]

sorry for being such a noob, but how do I check that? :) It should be 1 right?

[Ameer Hamza]

If you are inside a loop, you can use loop variable. If you are just using it alone, then you can write

exportgraphics(gca, 'file.png')

Either way, give a numeric value to i if you want to use that code.

[johndoe]

Ok, thanks. I would like to use it to save an image of a plot for each iteration. So I guess i should try to get it to work inside loop then? It's one of those red marks at the side of line that says: "invalid syntax at '.png A'('might be missing a closing ')' " Could it be something with that?

[Ameer Hamza]

Can you paste the exportgraphics line from your code. Make sure that it have same brackets as shown in my code.

[johndoe]

exportgraphics(gca, ['file' num2str(i)] '.png')

here it is.

[Ameer Hamza]

Correct the brackets

exportgraphics(gca, ['file' num2str(i) '.png'])

[johndoe]

really appreciate you taking the time helping me out :)

now I got this error message instead though, do you know what could be wrong?

Unrecognized function or variable 'exportgraphics'.

Error in Skript_haloklin_plots (line 23)
exportgraphics(gca,['file' num2str(i) '.png'])

[Ameer Hamza]

Which MATLAB are you using? If older than 2020a, the use the following line instead of exportgraphics

saveas(gcf, ['file' num2str(i) '.png'])

[johndoe]

yeah, it was 2019. Works great now. Thanks so much! :)

[Ameer Hamza]

Glad to be of help.

[mehmet durmaz]

thanks a lot.