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Principal component analysis (PCA) is a linear dimensionality reduction technique. It reduces a multivariate dataset to a smaller set of constructed variables preserving as much information (as much variance) as possible. These variables, called principal components, are linear combinations of the input variables.
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Scale before PCA [duplicate]
I'm using PCA from sckit-learn and I'm getting some results which I'm trying to interpret, so I ran into question - should I subtract the mean (or perform standardization) before using PCA, or is this … But one things still puts me in doubt - why scale when PCA considers the directions of greatest variance? Aren't I going to break this when standardizing the data before PCA? …
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Filter timeseries before PCA
Because of that, I need to do PCA. Some of the features are noisy, others are not.
My question is - does it make to do some kind of smoothing (filtering) such as moving average, before doing PCA? …
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PCA in case of multivariate time series
I have a dataset which contains multivariate time series and I would try applying PCA on it, but I'm not sure how to do it. … Would it make sense to extend my approach and just add samples from other time series in the dataset, and then run PCA on all of that? …
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Will I miss anomalies/outliers due to PCA?
I was planning to use PCA to reduce the dimensionality as to be able to notice such anomalies better. … But then I thought about it and made a counter example how PCA could even make things worse, even though the space has less dimensions.
Here's an example. …
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Standardization of "spiky" data
To be able to do so I'm performing PCA before clustering, and before that I'm performing standardization of my parameters. … As the normalization is not good, neither is the PCA and clustering of course suffers from parameters on different scale so clusters are hidden due to parameters on higher scale which act as "boosted". …