Saving plot as a GIF

Hello,

So I have written a script that takes data points and plots them over a certain x and then pauses and plots the next in a for loop. When I run it it looks great but now I want to save it as a gif and I have no idea how. It's basically lines that are plotted then erased and the next line is plotted. I tried using fanimate but I dont have a function I have data points. I will include my code for reference.

Thank you

%Opens the figure
figure(1)

%Finds the min and max vectors of the two matricies
miny = min(W1);
maxy = max(W1);

%Used to "animate" the matricies over the columns
for i = 1:501
    plot(x,W1(:,i), '-b', x,W2(:,i), '-r', 'LineWidth',3)
    axis off
    %Sets the axis mins and maxes
    axis([min(x) max(x) min(miny) max(maxy)])
    %Pauses after every i value to give the perception of animation
    pause(.001)
    
end

Answer 1

[Walter Roberson]

%This code assumes that you might be changing x inside your loop. If x is
%constant then it can be done a little better.

filename = 'MyAnimation.gif';

%Opens the figure
figure(1)

%Finds the min and max vectors of the two matricies
miny = min(W1); minminy = min(miny);
maxy = max(W1); maxmaxy = max(maxy);

H = plot(nan, nan, '-b', nan, nan, '-r', 'LineWidth', 3);
axis off

%Used to "animate" the matricies over the columns
for i = 1:501
    H(1).XData = x; H(1).YData = W1(:,i);
    H(2).XData = x; H(2).YData = W2(:,i);
    
    %Sets the axis mins and maxes
    axis([min(x) max(x) minminy maxmaxy])
    %Pauses after every i value to give the perception of animation
    pause(.001)
    F = getframe();
    if i == 1
        imwrite(F.cdata, F.colormap, filename, 'writemode', 'overwrite', 'DelayTime', 1/30);
        FrameSize = [size(F.cdata,1), size(F.cdata,2)];
    else
        imwrite( imresize(F.cdata, FrameSize), F.colormap, filename, 'writemode', 'append');
    end
    
end

Caution: when your x is not constant and you do not know ahead of time what the maximum and minimum possible x are, then you can run into situations where a captured frame might not be exactly the same size as previous frames. The imresize() of frames after the first frame ensures that particular problem cannot occur. But when it would have occurred, the frame might shift slightly visually -- the right border (especially) might flicker moving back and forth a few pixels.

This problem can be avoided if the x values are constant for all iterations, or at least if the minimum and maximum x and y are known ahead of time.