CODEWITHSUNDEEP
pythonscikit-learnnaivebayes
hory
hory

Reputation: 305

Dot product of sparse matrix

Im reading implementation of the Multinomial Naive Bayes and I do not understand how does this following calculation of dot product of the following matrixes work. 

self.feature_count_ += safe_sparse_dot(Y.T, X)

Code can be found here

Where Y.T.shape = (3, 7000) and X.shape = (7000, 27860). How can it work when number of rows in the Y.T is not equal to number of columns in X? The size of the resulting matrix is (3, 27860) ?? How does it work? What am I missing?

enter image description here enter image description here enter image description here

Upvotes: 0

Views: 78

Answers (1)

Luke
Luke

Reputation: 5564

Check out the "Mulitplying a matrix by another matrix" section here: https://www.mathsisfun.com/algebra/matrix-multiplying.html

If you go through the multiplication, you'll see that only the "inner" dimensions have to match (the 7000 in your case)

Upvotes: 1

Related Questions