How to use classification after PCA(dimensionality reduction)

Question

Kong 2020-3-25

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/512859-how-to-use-classification-after-pca-dimensionality-reduction

评论： Kong 2020-4-17

采纳的回答： Shishir Singhal

Hello.

I want to classify videos.

The original data : 25290 x 25

After applying dimensionality reduction like PCA, I got this data.

The reduced data : 2 x 25

Is it resonable to use these reduced data for classification?

I got low accuracy of classification. Could you give some ideas to solve it?

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Answer 1

Shishir Singhal 2020-4-9

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https://ww2.mathworks.cn/matlabcentral/answers/512859-how-to-use-classification-after-pca-dimensionality-reduction#answer_424965

Don't use PCA for dimentionality reduction or feature selection in case of videos or images. Instead use some feature extraction techniques in images like HOG features, sift features, optical flow(for videos), etc. Since the datapoints are very less(assuming 25 datapoints), you could use some data augementation techniques for videos.

For example, crop some random sequence from the video for temporal augmentation then use Image augmentation for each frame.

For Image augmentation, you can refer to documentation here: https://www.mathworks.com/help/deeplearning/ref/imagedataaugmenter.html

Hope it helps !!! :)