Convert the mxn size Matrix to square Matrix without using loop or if

Hi,

I have a random mxn matrix, like 4x6 and I want it to be square. For example, a original 4x6 matrix would be created by deleting the first and second column to a formed a 4x4 matrix.

A =

      0.8147    0.6324    0.9575    0.9572    0.4218    0.6557
      0.9058    0.0975    0.9649    0.4854    0.9157    0.0357
      0.1270    0.2785    0.1576    0.8003    0.7922    0.8491
      0.9134    0.5469    0.9706    0.1419    0.9595    0.9340

B = 
   0.9575    0.9572    0.4218    0.6557
   0.9649    0.4854    0.9157    0.0357
   0.1576    0.8003    0.7922    0.8491
   0.9706    0.1419    0.9595    0.9340

How can I create from A to B without using loop or if-statment? and it should be work for all mxn, which m and n could be any number.

I started like this but got stunned. [m n] = size(A);

newA(m,:) = [];
newA(:,n) = [];

Thanks

Answer 1

[Geoff Hayes]

David - if you want to convert your (say) 4x6 matrix into a 4x4 by removing the first two columns, then you could do something like

 B = A(:,3:end);

In the above, we use the colon to mean "all rows", and the 3:end to mean "get columns 3 through to the end". You can extend this to other (different sized) matrices.

EDIT

In your code where you try to set the mth row to the empty matrix, and the nth column to the empty matrix

 newA(m,:) = [];
 newA(:,n) = [];

what you really want to do is to set the first two columns to be the empty matrix which has the effect of removing them. Try

 newA = A;
 newA(:,1:2) = [];

[david Chan]

I know I can do

B = A(:,3:end);

to removing the coulumns that I want, However, I have to write a script which satisfies any random mxn matrix

[Geoff Hayes]

If your matrix is an mxn, with n>m, then you can do

 B = A(:,m-n+1:end);

And if m>n, then presumably you still want an nxn matrix but with n rows. So try

 B = A(m-n+1:end,:);

[david Chan]

its working now, thank you

Answer 2

[Image Analyst]

Try this:

clc;
A =[...
      0.8147    0.6324    0.9575    0.9572    0.4218    0.6557
      0.9058    0.0975    0.9649    0.4854    0.9157    0.0357
      0.1270    0.2785    0.1576    0.8003    0.7922    0.8491
      0.9134    0.5469    0.9706    0.1419    0.9595    0.9340]
[rows, columns] = size(A);
if rows > columns
  % Delete rows.  Take bottom-most rows
  numRowsToDelete = rows - columns
  newA = A(numRowsToDelete+1:end, :)
elseif rows < columns
  % Delete columns
  numColumnsToDelete = columns - rows
  newA = A(:, numColumnsToDelete+1:end)
end

[david Chan]

I cannot use any if-statement

[david Chan]

it works for me tho