Question

how is it possible to assign certain color to a value from matrix.
For example I have a 10by10 matrix with values from 0 to 9.
Afterwards I’d like to get a “chess board” where 0 = white, 1 = black, 2 = blue…etc…

2nd question
if I run some operations where my matrices change with each loop and I run let’s say 10 lops (k = 10) – is it possible to make a video out of this 10 plot pictures I’ll be getting after each loop. (I’m programming some kind of cellular automaton, so I’d like to see how the situation changes over time).

Thanks

Answer 1

Consider this example:

%# lets create a 10-by-10 matrix, of values in the range [0,9]
M = fspecial('gaussian',10,2.5);
M = (M-min(M(:))) ./ range(M(:));
M = round(M*9);

%# prepare video output
vid = VideoWriter('vid.avi');
vidObj.Quality = 100;
vid.FrameRate = 5;
open(vid);

%# display matrix
h = imagesc(M);
axis square
caxis([0 10])
colormap(jet(10))
colorbar

%# capture frame
writeVideo(vid,getframe);

%# iterate changing matrix
for i=1:50
    M = rem(M+1,10);          %# circular increment
    set(h, 'CData',M)         %# update displayed matrix

    writeVideo(vid,getframe); %# capture frame

    drawnow                   %# force redisplay
end

%# close and save video output
close(vid);

You can use a custom colormap, simply create a matrix cmap of size 10-by-3, each row contains the RGB values, and pass it to the call colormap(cmap)

---

For MATLAB versions older than R2010b, you can use the avifile function, instead of VideoWriter:

%# prepare video output
vid = avifile('vid.avi', 'fps',5, 'quality',100);

%# iterations
for i=1:50
    %# ...

    %# capture frame
    vid = addframe(vid, getframe(gcf));

    drawnow
end

%# close and save video output
vid = close(vid);