Multivariate data analysis
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Transcript of Multivariate data analysis
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Principal Component Analysis (PCA)
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Principal Component Analysis (PCA)
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Principal Component Analysis (PCA)
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Principal Component Analysis (PCA)
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Principal Component Analysis (PCA)
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Principal Component Analysis (PCA)
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Principal Component Analysis (PCA)
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Principal Component Analysis (PCA)
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Principal Component Analysis (PCA)
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Principal Component Analysis (PCA)
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Alternative Derivation (PCA)
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Alternative Derivation (PCA)
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Alternative Derivation (PCA)
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Alternative Derivation (PCA)
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Singular Value Decomposition
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Singular Value Decomposition
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Singular Value Decomposition
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Example 1Use the data set "noisy.mat" available on your CD. The data set consists of 1965, 20-pixel-by-28-pixel grey-scale images distorted by adding Gaussian noises to each pixel with s=25.
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Example 1Apply PCA to the noisy data. Suppose the intrinsic dimensionality of the data is 10. Compute reconstructed images using the top d = 10 eigenvectors and plot original and reconstructed images
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Example 1If original images are stored in matrix X (it is 560 by 1965 matrix) and reconstructed images are in matrix X_hat , you can type in colormap gray and thenimagesc(reshape(X(:, 10), 20 28))imagesc(reshape(X_hat(:, 10), 20 28))to plot the 10th original image and its reconstruction.
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Example 2
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Example 2Load the sample data, which includes digits 2 and 3 of64 measurements on a sample of 400. load 2_3.mat
Extract appropriate features by PCA
[u s v]=svd(X','econ');
Create data
Low_dimensional_data=u(:,1:2);Observe low dimensional dataImagesc(Low_dimensional_data)