Question

1. Given a matrix variable "mat", write code using for loops, if statements, etc. that will accomplish the same as the following:

matsum = sum(mat')

Please make sure to store the result in "matsum" and dont use sum.

This is what I have so far but it keeps telling me is wrong....

% mat has been initialized for you:

mat = randi([-100,100],randi([15,20]),randi([15,20]));

% write your statements that accomplish the code above:

[r c]=size(mat);

for i=1:c

matsum=0;

for j=1:r

matsum=matsum+mat(j,i);

end

fprintf('Sum of column %d:',i)

disp(matsum);

end

Answer 1

• The main point to remember here is that sum of a matrix is the sum of each of its columns. Sum of transpose should be the sum of each of its rows.
• What was happening before is that with mat(j, i), the entries of each column were being added when it should be rows. Changing it to mat(i, j) works.
• Also, first for-loop should be for rows and second for columns. That way, we stay at one row and add all its entries, which is what's needed here.

Please find the matlab code below for sum of transpose of a matrix.

% matrix initialization mat = randi([-100,100],randi([15,20]),randi([15,20])); % Expected output: disp(sum(mat')); % Rows = 20, Columns = 18 [r c] = size(mat); % Traversing through rows. for i = 1:r matsum = 0; % Traversing through columns. for j = 1:c % Add the entries of each row. matsum = matsum + mat(i, j); end fprintf('Sum of column %d:', i) disp(matsum); end