Linked Questions
14 questions linked to/from What exactly is called "principal component" in PCA?
1 vote
0 answers
3k views
*Why* are eigenvectors the principal components in Principal Component Analysis? [duplicate]
I am confused as to why eigenvalues are the principal components. What is the intuition behind finding the eigenvectors of the covariance matrix for PCA?
4 votes
0 answers
2k views
What exactly is a Principal component and Empirical Orthogonal Function? [duplicate]
I am trying to enhance the contrast in the images I get after scanning a surface using Thermography (Principal Component Thermography ~Rajic, which is basically an application of Principal Component ...
1 vote
1 answer
379 views
Principal Components Analysis Terminology [duplicate]
I've been studying PCA, and some of the terminology isn't very clear. I do not understand what they mean when they refer to a "principal component". One definition I have seen calls it the new ...
2 votes
0 answers
54 views
Are the terminologies of score and principal component in PCA equivalent? [duplicate]
I am confused with the terminologies of score and principal component in PCA, it seems they are equivalent but there is also some difference. Could anyone explain to me?
639 votes
5 answers
536k views
Relationship between SVD and PCA. How to use SVD to perform PCA?
Principal component analysis (PCA) is usually explained via an eigen-decomposition of the covariance matrix. However, it can also be performed via singular value decomposition (SVD) of the data matrix ...
113 votes
5 answers
247k views
Loadings vs eigenvectors in PCA: when to use one or another?
In principal component analysis (PCA), we get eigenvectors (unit vectors) and eigenvalues. Now, let us define loadings as $$\text{Loadings} = \text{Eigenvectors} \cdot \sqrt{\text{Eigenvalues}}.$$ I ...
17 votes
1 answer
11k views
How does "Fundamental Theorem of Factor Analysis" apply to PCA, or how are PCA loadings defined?
I'm currently going through a slide set I have for "factor analysis" (PCA as far as I can tell). In it, the "fundamental theorem of factor analysis" is derived which claims that the correlation ...
8 votes
2 answers
26k views
Correlation between an original variable and a principal component
I am looking at this link http://strata.uga.edu/8370/lecturenotes/principalComponents.html where it says In interpreting the principal components, it is often useful to know the correlations of ...
7 votes
2 answers
4k views
Is principal component regression (PCR) using principal component scores for regression?
Principal component regression (PCR) in fact is regression on PC scores but not PCs. Why then in so many books and tutorials do they say something like, in statistics, principal component ...
7 votes
1 answer
10k views
Difference between principal directions and principal component scores in the context of dimensionality reduction
I have performed principal component analysis (PCA) of data matrix $X$ by doing singular value decomposition (SVD) $$ X = U S V', $$ where the columns of $V$ are the principal directions/axes and the ...
3 votes
1 answer
5k views
A problem with interpretation of principal components as linear combinations of features
I often see the principal components of PCA described as "linear combinations of the original features". Say we want to compute the principal components of our $m \times n$ design matrix $A$ ($m$ ...
2 votes
1 answer
2k views
Computing scalar/dot product between principal component and data
I am very new to R and statistics so this may be a simple question. I have a matrix (1000,756) containing 1000 years of winter sea-level pressure data (SLP) at 756 locations in the North Atlantic. I ...
0 votes
1 answer
949 views
Can someone explain the simple intution between Principal component 1, 2, ... etc in PCA? [duplicate]
I see that in PCA the first principal component maximizes the variances amongst all the points within the data set. What exactly does this mean, what does it show and what does every other principal ...
2 votes
1 answer
126 views
Can PCA factors be correlated?
Are principal factors in principal component analysis always uncorrelated, or can they end up being correlated? If so, how and why?