Week1 final lab exercise 2

Course Q&A Machine Learning Specialization Advanced Learning Algorithms
1

Shouldn’t the thing in the red box be XT*W?

image
image1056×714 62.4 KB

2

Nope, because X is already filled with the row matrices x_i^T, instead of the original column matrices x_i.

Cheers

3

If you’re expecting consistency in how the X and W matrices are organized (rows vs. columns), you will be disappointed.

There is no universal standard for this, even within the same course.

4

I see why you might think it should be XTW, but actually, it’s not because the matrix inside the red box is already filled with the row matrices, not the column ones. The way the data is structured here means that the operation is different from what you’d expect with XTW. It’s a subtle detail, but that’s why it’s set up like this.

5

Thanks for the reply DriftLau! But your comment actually got me confused with rmwkwok’s comment because he confirmed with my thinking that X is already filled with row matrices. So no X.T is necessary here.

6

Hello, @DriftLau,

Should the “not” in the quote above be removed? Because the sentence structure is a bit odd: “it’s not because … row matrices, not the column ones”

Cheers,
Raymond