MATLAB: Is there a function to sum 1:n matrices of same size

matrix sum

I have,

n=user input
a=sum(matrix 1 to n)=element by element addition for matrices 1 to n to give a matrix of the same size.

I have tried a=sum(matrix{1:n}) with no luck.

Your notation suggests that your matrices are being held in a cell array matrix{i}, i=1...n. If I continue to assume this,

sum(cat(3,matrix{:}),3)

Just add a dimension to A, then:

A(:,:,1)= %3x3 matrix
A(:,:,2)= %3x3 matrix ...
sumA=sum(A,3);

Your code is buggy, and that concept will fail for 3D arrays. Try this instead:

isrow(v) && numel(v)==3

isequal(size(v),[1,3])

Lets look at the bug in your code. First note that the LHS will always be true, as no value is zero:

>> all([1,3])
ans = 1

So the LHS is always equal to 1, which you then compare against the size of v:

>> v = 1:4;
>> all([1,3])==size(v)
ans =
  1  0
>> 1==size(v) % exactly equivalent

ans =
  1  0

this will never be all true (which if requires if the condition is non-scalar), unless v is a scalar:

>> v = 4;
>> all([1,3])==size(v)
ans =
  1  1
>> 1==size(v) % exactly equivalent
ans =
  1  1

The error was putting the parenthesis in the wrong place, it should have been right at the end:

all([1,3]==size(v))

but note that this will still fail for ND arrays. The code at the top of this answer will work for any size array.