# How can I solve it: Matrix dimensions must agree.

2 views (last 30 days)
Aimee Jin on 25 Oct 2020
Commented: Walter Roberson on 25 Oct 2020
function A = matrixCSums(M)
% M is a numeric matrix and A has the same size as M.
% Each element in A is the sum of the corresponding element in M and all
% the elements above it. Example:
% M = [ 1 3; ... A = [ 1 3; ...
% 4 5; ... 5 8; ...
% -7 2] then -2 10]
% Do NOT use any built-in functions other than size
if M ==[]
A=[];
else
A(1,:)=M(1,:); %initial row of A
[nr,nc]=size(M);
for i=2:nr
A(i,:)=A(i-1,:)+M(i,:);
end
end
When I call the function:
M = [ 1 3; 4 5; -7 2];
A = matrixCSums(M)
it says:
Error using ==
Matrix dimensions must agree.
Error in matrixCSums (line 9)
if M ==[]

Alan Stevens on 25 Oct 2020
Replace
if M ==[]
with
if isempty(M)

drummer on 25 Oct 2020
if M == []
A(M == []) = [];
else
% rest of your code here.
end
Hope that helps.
Cheers

#### 1 Comment

Walter Roberson on 25 Oct 2020
M == [] is going to fail unless M is empty (but will work if M is a different size of empty).