Building a 2x2 Matrix with one for-loop

A friendly hello :)

I actually got a simple question. Looking at the folling code:

k=1;
for i= 1:4

      M(k,:)=i+[2 3 4];
      k=k+1;

end

This will create a 4x3 Matrix looking like:

M =

       3     4     5
       4     5     6
       5     6     7
       6     7     8

So, but without doing " M' " (transpose) at the end, how can I switch rows and columns?? In other words: I tried this:

    M(:,k)=i+[2 3 4];

So that the Matrix builds up column-wise into a 3x4 Matrix. but it doesn't work. why??

Kind regards

ps: only for interests: I got the problem from this. I try to compare one list of words, with one other.

k=1;
for i=1:100000
    test(k,:)=strncmp(words(i),word_list,3);
    k=k+1;
end

naturally " strncmp(words{s(i)},word_list,3) " gives a column-vector, because my word_list is a column (imported from a text file). but here, each result of "strncmp" lines up in a row. my problem is: it is just very confusing !

   test(:,k)=strncmp(words(i),word_list,3); %does not work

(again, I could just transpose at the end, but this transposing takes noticely the longest time. that's why I removed it and I am curious, if there is no way in already building up the Matrix the correct way. or the way I want.)

Answer 1

[Image Analyst]

Try this:

% First way:
for k= 1:4
      M(k,:)=k+[2 3 4];
end
M

% Second way:
clear('M');  % Need to clear it if in the same script.
for k= 1:4
      M(:,k)=k+[2; 3; 4];
end
M

You don't need the k counter. And it's also bad practice to use i (the imaginary variable) as a loop counter so I switched it to k. Your other problem was not having semicolons in the vector to make sure it was a column vector instead of a row vector . The result:

M =
     3     4     5
     4     5     6
     5     6     7
     6     7     8
M =
     3     4     5     6
     4     5     6     7
     5     6     7     8

Answer 2

[Florian]

thank you very much !! it works. and also thanks for the advice. I will change my loop counters in future :)