Looping through cell array in order

I'm drawing squares on a grid. The squares need to have an ID as set within a cell array. I was expecting the ID to loop through each ID in the cell in order by instead it cycles through in rows.

&nbsp

    cell_id = cell(1, 2); % 1 x 5 cell array
    cell_id{1, 1} = 1365; 
    cell_id{1, 2} = 1256; 
    cell_id{1, 3} = 6214;     
    cell_id{1, 4} = 2587; 
    cell_id{1, 5} = 1564;

    hold on

    for i = 1:2:12
        count = 1;
        for ii = 1:2:12

            plot(1*i , 1*ii, 's', 'MarkerSize', 50);

            if (count <= 5)
                id = cell_id(1,count);
                text(1*i, 1*ii, ['ID:',id]);
                count = count + 1;
            elseif (count > 5)
                id = cell_id(1,1);
                count = 1;
                text(1*i, 1*ii, ['ID:',id]);
            end
        end
    end

Any ideas, thanks.

[per isakson]

• Do you expect 4 rows times 6 columns of boxes?
• Replace i by xx and ii by yy or something associated with directions
• Set the axes limits before adding the boxes. It's confusing that the limits change all the time
• And format the code properly. (I did it this time.)

Answer 1

[Guillaume]

You appear to be a bit confused about a few things:

cell_id = cell(1, 2);

declares a 1 x 2 cell array, not a 1 x 5. Anyway, you could replace your first two lines with:

cell_id = {1365, 1256, 6214, 2587, 1564};

Secondly, you reset your count for each column, since it's set to one in the first for loop. You probably meant to do the assignment to 1 before the first loop.

Also, use more descriptive variables than i and ii. row and col would be better.

To sum it up:

figure; axis off; hold on;
cell_id = {1365, 1256, 6214, 2587, 1564};
count = 1;
for col = 1:2:12
  for row = 1:2:12
     plot(col, row, 's', 'MarkerSize', 50);
     text(col, row, sprintf('ID:%d', cell_id{count}));
     count = mod(count, numel(cell_id)) + 1;
  end
end

[Josh]

Got really confused, this is really neat/optimised. Thanks

[Josh]

Guillaume, I just noticed if I change the amount of IDs to only three it just loops the same ID for each row again

cell_id = {1365, 1256, 6214};

If I have 4 it does change but misses a random ID out it only works fully on 5 IDs.

Any suggestions? Thanks

[Guillaume]

Works fine for me with 3 and 4 IDs.

However, be aware of the coordinate system used by plot and text in my code (which is the same as in your original code). The IDs are printed starting at the bottom left corner of the figure, going up the column and then up the next column on the right and so on.

Rereading your original question it looks like you wanted to start in the upper left corner and go along the rows rather than the columns. You need to change the for loop accordingly:

for row = 11:-2:1
  for col = 11:-2:1

[Josh]

Hmm ... this code

figure; axis off; hold on;
cell_id = {1365, 1256, 6214};
count = 1;
for col = 12:-2:1
  for row = 12:-2:1
     plot(col, row, 's', 'MarkerSize', 50);
     text(col, row, sprintf('ID:%d', cell_id{count}));
     count = mod(count, numel(cell_id)) + 1;
  end
end

Produces the same ID

Can you replicate this? Does it work for you?

[Guillaume]

I wrote:

for row = 11:-2:1
   for col = 11:-2:1

Note the order of the variables. row first, col second. With your code you go down the column, since there are 3*n rows, when you go back to the next column, your back to your first ID when there are only three of them.

If you swap row and col as above, you go along the rows and wrap back at the beginning of a row.

[Image Analyst]

I see no reason for a cell array at all. What about this requires cells instead of a simple numerical array?

[Josh]

Oops, perfect thanks. Good explanation