PCA to reduce dimensionality of feature vector

Question

Nazeera Sheth 2017-12-18

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https://ww2.mathworks.cn/matlabcentral/answers/373550-pca-to-reduce-dimensionality-of-feature-vector

回答： Matlaber 2019-2-19

I have a feature vector of size 4096x180 ( 180 samples ). I want to reduce the dimensionality using PCA. I have looked at various codes available but not able to apply it. How do I write the code in Matlab 2014?

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Answer 1

Mohammad Haghighat 2018-1-25

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https://ww2.mathworks.cn/matlabcentral/answers/373550-pca-to-reduce-dimensionality-of-feature-vector#answer_301772

Please check the Matlab's pca command:

https://www.mathworks.com/help/stats/pca.html

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Answer 2

Matlaber 2019-2-19

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https://ww2.mathworks.cn/matlabcentral/answers/373550-pca-to-reduce-dimensionality-of-feature-vector#answer_361810

在 MATLAB Online 中打开

I just want to have a simple PCA to reduce my dimensionality of let say 400 * 5000 to 400 * 4

meaning reduce from 5000 to 4.

I am not sure where can I set the value of reduction.

coeff = pca(X)

I am trying to follow:

load hald

Then:

The dataset of ingredient is 13 * 4

coeff = pca(ingredients)

Output:

 coeff = 4×4
   -0.0678   -0.6460    0.5673    0.5062
   -0.6785   -0.0200   -0.5440    0.4933
    0.0290    0.7553    0.4036    0.5156
    0.7309   -0.1085   -0.4684    0.4844

I am wondering can i change it to output of 13 *2 (13 x 2)