# Multiplication of sparse matrix and a normal matrix

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Amit Chakraborty on 25 Sep 2021
Answered: Amit Chakraborty on 25 Sep 2021
I have a Sparse Matrix : S
The size of S is : 196608x4096 sparse double
and the normal (Non Sparse) matrix : D
The size of D is : 196608x1 single
Matrix D is full of one . [ means : D= ones(196608,1 )]
I want to multiply them both >> transpose(S)* D;
But showing me some error :
1. " Error using .* Sparse single array arithmetic operations are not supported."
2. " Error using * MTIMES (*) is not supported for one sparse argument and one single argument "
Even I tried to convert the matrix D into sparse but showing me following error :
" Error using sparse Input matrix must be double or logical".
Any kind of suggestions to solve this problem will be appreciated.
Thank You !!!
Happy Weekend !!!

Walter Roberson on 25 Sep 2021
You are trying to multiply a sparse double precision matrix by a non-sparse single precision matrix.
If you are expecting:
• sparse double result: use S.' * double(D)
• sparse single result: not permitted. sparse matrices can only be double precision or logical
• full double result: use full(S.' * double(D))
• full single result: use full(S.' * D)

David Goodmanson on 25 Sep 2021
Hi Amit,
sum(S)'
where the result is still sparse, or
full(sum(S)')
if you want a regular vector at that point.
Amit Chakraborty on 25 Sep 2021
I do not want to convert into "full". Because above matrix is just example. Converting into "full" will takes lot of memory.

Amit Chakraborty on 25 Sep 2021
Thank you Both. I have learnt a new thing from you guys.