How do I get the deletedElems to form its own column array? I got newMatrixA, but deletedElems keeps getting an output of 2 instead of [ 1; 3; 2; 9; 7; ]

function [ newMatrixA, deletedElems ] = DeleteRowColumn( origMatrixA, delRow, delCol )
% DeleteRowColumn: Delete the row and column specified by delRow
% and delCol from input matrixA and returns the modified matrix and
% the deleted elements as a column array.
%   Inputs: origMatrixA - input matrix
%           delRow - row to delete
%           delCol - column to delete
%
%   Outputs: newMatrixA - input matrix with specified row and column deleted 
%            deletedElems - deleted elements from input matrix
%                           returned as a column array

      % Assign newMatrixA with origMatrixA
      newMatrixA = origMatrixA;

      % Assign deletedElems with row of newMatrixA to be deleted 
      % (Hint: Use the transpose operator to convert a row to a column)
      delRow = delRow(:)';
      deletedElems = delRow;  

      % Remove row delRow from newMatrixA
      newMatrixA(deletedElems,:) = [];    

      % Append deletedElems with the with column of newMatrixA to be deleted
      deletedElems = delCol;  % FIXME

      % Remove column delCol from newMatrixA
      newMatrixA(:,deletedElems) = [];    % FIXME

end

Answer 1

[Jan]

Wanted: deletedElems - deleted elements from input matrix returned as a column array

function [ newMatrixA, deletedElems ] = DeleteRowColumn( origMatrixA, delRow, delCol )

% Assign newMatrixA with origMatrixA
newMatrixA = origMatrixA;

% Assign deletedElems with row of newMatrixA to be deleted 
% (Hint: Use the transpose operator to convert a row to a column)  *Strange hint?!*
tmp          = newMatrixA(delRow, :);
deletedElems = tmp(:);

% Remove row delRow from newMatrixA
newMatrixA(delRow,:) = [];    

% Append deletedElems with the with column of newMatrixA to be deleted
tmp          = newMatrixA(:, delCol);  % [EDITED]
deletedElems = cat(1, deletedElems, tmp(:));

% Remove column delCol from newMatrixA
newMatrixA(:, delCol) = [];
end

Or using logical indexing:

function [ newMatrixA, deletedElems ] = DeleteRowColumn( origMatrixA, delRow, delCol )

mask            = false(size(origMatrixA));
mask(delRow, :) = true;
mask(:, delCol) = true;

deletedElems = origMatrixA(mask);
newMatrixA   = reshape(origMatrixA(~mask), max(sum(mask, 1)), []);
end

[Hena Patel]

There was a small syntax error with this line [tmp = newMatrixA(delCol, :);] but other than that it worked.

I know the code works, but can you briefly explain what this line does: deletedElems = cat(1, deletedElems, tmp(:));

[Jan]

@Hena: cat concatenates the arguments along the the dimension specified as the first argument. cat(1, a, b) is the same as [a;b] . Then the line

deletedElems = cat(1, deletedElems, tmp(:))

appends the elements from removing the columns to the existing list of elements, which have been removed before.

[Kemuel Roberts]

this was extremely helpful.