For-loop matrix where the elements increase by 1

Hey all, I need to make a 6x5 matrix from 1:30. so far I have this:

c = 1;

d = 1;

count = 1;

for row = 1:6;

      for col = 1:5;
          A(row,col) = c,d;
          c = c + 1;
          d = d + 1;
          count = count + 1;
          if count>30;
              break
          end
      end
  end

This is successful at producing the matrix, however the matrix shows up 30 times when I run the script. How do I make it only show up once? Thanks!

Answer 1

[Jan]

The elements increase by 1. This leaves some degrees of freedom: Should the increasing be row-wise or column-wise? What is the start value?

I all cases this will help:

c = 1;   % Start value
for row = 1:6
  for col = 1:5
    c = c + 1
  end
end

I leave it up to you to fill this into your array.

Note that this can be done more efficiently in Matlab without loops. You need only 1:30 and the reshape function.

[Alana Duffy]

Thanks for the prompt response!

I made a bit of process before seeing your answer. The matrix is meant to start at 1, increase by 1 across a row and stop at 30. now the only issue I am having is making the matrix appear once rather than 30 times.

This is the code I have:

c = 1;

d = 1;

count = 1;

for row = 1:6;

      for col = 1:5;
          A(row,col) = c,d;
          c = c + 1;
          d = d + 1;
          count = count + 1;
          if count>30;
              break
          end
      end
  end

[Walter Roberson]

The line

            A(row,col) = c,d;

is equivalent to

            A(row,col) = c
            d;

which assigns c into that position of array A, displays the result of the assignment, and then calculates d and throws away the result of the calculation of d because of the semi-colon after it.

The line does not store the pair of values [c, d] into the location A(row,col). Numeric arrays like your A cannot store multiple values in the same location. You would need

             A(row,col) = {[c,d]};

or

             A{row,col} = [c,d];

to store the pair of values in the single location in A, which would have to be a cell array.

[Jan]

I do not understand, why you use 3 counters: counter, c, d. As far as I understand one counter is sufficient already. The loops stops after 5*6=30 iterations at all, so there is no need for a break:

c = 1;
for row = 1:6
    for col = 1:5
        A(row,col) = c;
        c = c + 1;
    end
end