Hey Guys,

Can anyone help me out with the “Understanding the transformation model pcaTr” section?

In this section, it is mentioned that “`pcaTr.components_`

has the rotation matrix”, however, the values stored in `pcaTr.components_`

ae as follows:

[[-0.70710678 -0.70710678]

[-0.70710678 0.70710678]]

So, shouldn’t the rotation matrix be as follows:

[[-cos(45) -sin(45)]

[-sin(45) cos(45)]]

which is different from the one mentioned in the lab. Also, it is mentioned that “First row must be in the direction of [1, n]”, but for `n = 1`

, isn’t the first row of the rotation matrix in the direction of `[-1 -n]`

. Am I misinterpreting something, if so, please do let me know.

### Update #1

In the next section, it is mentioned that “In theory, the Eigenvector matrix must be the inverse of the original rotation matrix”. This also means that the “inverse of the Eigenvector matrix must be the original rotation matrix”. So, even I take the inverse of the above Eigenvector matrix, I should get the rotation matrix as follows:

[[-0.70710678 -0.70710678]

[-0.70710678 0.70710678]]

which is once again not equal to the rotation matrix mentioned in the lab.

### Update #2

In Week 4 lab entitled “Rotation matrices in R2”, the rotation matrix is given as

[[-cos(A) -sin(A)]

[-sin(A) cos(A)]]

where A = \theta; I am a little confused as to whether the rotation matrix can have a single possible configuration, or multiple different configurations.

Thanks,

Elemento