Looping through columns and rows without using Indexing in matlab - matlab

Question

I'm fairly new to matlab and I'm currently working on MATLAB to create a loop that will go through each column and each row and then increment A and B as it goes. I know that there's indexing which you can do but I'd like to learn how to do it step by step. I've come up with the pseudo code for it but I'm struggling with the actual syntax in MATLAB to be able to do it.
Pseudocode:
For columns i 1-300;
Increment A
For rows j 1-4
Increment B
End
End
My actual code that I've been trying to get to work is:
%testmatrix = 4:300 Already defined earlier as a 4 row and 300 column matrix
for i = testmatrix (:,300)
for j = testmatrix (4,:)
B=B+1
end
A=A+1
end
I'm not 100% sure how I'm supposed to format the code so it'll read testmatrix(1,1) all the way through to testmatrix (4,300).
Any help would be greatly appreciated!

Answer 1

You could let it run through the first row to get the right column, then through that column. But you can't feed your running value from the matrix:
[rows cols] = size(testmatrix); %// rows=4, cols=300
for i = 1:cols
for j = 1:rows
temp = testmatrix (j,i); %// contains the element of your matrix at (j,i)
B=B+1;
end
A=A+1;
end
The semicolons ; suppress the output to the command line. Remove them if you want to output A and B at each step.
Here, temp will cycle through the elements (1,1) through (4,300) and you can do whatever you want with them. Note that this is generally an inefficient way to do most things. Matlab supports greatly efficient vectorized calculations, which you should use. But unless I know what exactly you're trying to achieve, I can't really help you with that. (If all you want is A and B's final values, it's as easy as A=A+cols;B=B+cols*rows;.)