2. Problem: PCA with some analytical skills related questions. Consider the general PCA problem: Given a matrix of data, X of size p × N (p < N), we want to find the "best" approximation (in the average norm square sense) of xi≈µ+Vqλi, where V, is a unitary px q (q< p) matrix, and λ; a q x 1 vector, where x is the ith column of X. Denote the eigenvalues of XXT by V1, V2, ... ,Vp, in descending order. (a) Explain what happens to the PCA analysis, if xk = V₁, for some k in {1,2,,N}. In other words, what happens to the approximation of X? Note that v₁ is the eigenvector of XXT that corresponds to its maximum eigenvalue. (b) Describe what happens to PCA, if eigenvalues of XX v₁ = 0, for ≥ 91, with and q₁ > q. In other words, is the accuracy of the PCA better? 91
2. Problem: PCA with some analytical skills related questions. Consider the general PCA problem: Given a matrix of data, X of size p × N (p < N), we want to find the "best" approximation (in the average norm square sense) of xi≈µ+Vqλi, where V, is a unitary px q (q< p) matrix, and λ; a q x 1 vector, where x is the ith column of X. Denote the eigenvalues of XXT by V1, V2, ... ,Vp, in descending order. (a) Explain what happens to the PCA analysis, if xk = V₁, for some k in {1,2,,N}. In other words, what happens to the approximation of X? Note that v₁ is the eigenvector of XXT that corresponds to its maximum eigenvalue. (b) Describe what happens to PCA, if eigenvalues of XX v₁ = 0, for ≥ 91, with and q₁ > q. In other words, is the accuracy of the PCA better? 91
Linear Algebra: A Modern Introduction
4th Edition
ISBN:9781285463247
Author:David Poole
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Chapter6: Vector Spaces
Section6.2: Linear Independence, Basis, And Dimension
Problem 3AEXP
Related questions
Question
![2. Problem: PCA with some analytical skills related questions.
Consider the general PCA problem: Given a matrix of data, X of size p × N
(p < N), we want to find the "best" approximation (in the average norm square
sense) of xi≈µ+Vqλi, where V, is a unitary px q (q< p) matrix, and λ; a
q x 1 vector, where x is the ith column of X. Denote the eigenvalues of XXT
by V1, V2, ... ,Vp, in descending order.
(a) Explain what happens to the PCA analysis, if xk = V₁, for some k in
{1,2,,N}. In other words, what happens to the approximation of X?
Note that v₁ is the eigenvector of XXT that corresponds to its maximum
eigenvalue.
(b) Describe what happens to PCA, if eigenvalues of XX v₁ = 0, for ≥ 91,
with and q₁ > q. In other words, is the accuracy of the PCA better?
91](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F833bf7b1-3e6b-4749-8e88-54090320a3f5%2F1e7b23a8-6dd4-4925-92b3-74b090d19318%2Fljr5inm_processed.png&w=3840&q=75)
Transcribed Image Text:2. Problem: PCA with some analytical skills related questions.
Consider the general PCA problem: Given a matrix of data, X of size p × N
(p < N), we want to find the "best" approximation (in the average norm square
sense) of xi≈µ+Vqλi, where V, is a unitary px q (q< p) matrix, and λ; a
q x 1 vector, where x is the ith column of X. Denote the eigenvalues of XXT
by V1, V2, ... ,Vp, in descending order.
(a) Explain what happens to the PCA analysis, if xk = V₁, for some k in
{1,2,,N}. In other words, what happens to the approximation of X?
Note that v₁ is the eigenvector of XXT that corresponds to its maximum
eigenvalue.
(b) Describe what happens to PCA, if eigenvalues of XX v₁ = 0, for ≥ 91,
with and q₁ > q. In other words, is the accuracy of the PCA better?
91
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