PCA apply: recover expressed variance as a variable

[l.thomas]

Hey there,
I use the PCA apply with a fixed number of dimensions (let say 3) which shows a % for the information preservation (or expressed variance).
Is there a way to recover this information into a variable ? e.g. to report it later
The flow variable panel as a field for the information fraction but it returns the value in the grayed field below

Thanks !

[stelfrich]

Hi @l.thomas,

@l.thomas

Is there a way to recover this information into a variable ? e.g. to report it later

You are right that this information is currently not provided as a flow variable. If I am not mistaken, you can compute this by summing up all the eigenvalues (first column of Spectral Decomposition table=second output port of PCA Compute) and computing the fraction of the sum of the eigenvalues up to the dimension that is taken into account (starting from the top of the table since it is ordered by magnitude of eigenvalues) and the overall sum. For instance, going from 5 to 3 dimensions: (E0 + E1 + E2) / (E0 + … E4), where E0 is the eigenvalue with the greatest magnitude.

Longer term, this is something that could be provided as a flow variable: I have created a ticket for that!

Best,
Stefan