Linked Questions

7
votes
4answers
5k views

Is it acceptable to reverse a sign of a principal component score? [duplicate]

I have two datasets from similar psycholinguistic experiments. In both of them, information about the participant's reading and spelling ability was collected, then converted into standardized scores ...
1
vote
1answer
889 views

Reverse the sign of PCA [duplicate]

I'm struggling on getting a good explanation for the unexpected signs of Principal Component for months. I tried to replicate a result and I got exactly the opposite signs for all components. While I ...
2
votes
2answers
794 views

How does pca() function in Matlab fix the sign of principal components? [duplicate]

PCA gives me loadings with different signs. I understand that I may simply revert them (as explained in this thread), but I need an explanation (my boss insists) of why Matlab implementation gives me ...
4
votes
1answer
983 views

Is the sign of principal components meaningless? [duplicate]

Does the sign of the vectors returned by PCA have any significance after I center my variables?
1
vote
0answers
348 views

Is it possible to reverse the sign of factor loadings for one factor? [duplicate]

I just want to confirm if it is possible to reverse the sign (+/-) on the factor loadings of one factor. I run a PAF with Oblimin rotation. I obtained 6 factors but in one of them the items that load ...
0
votes
0answers
325 views

EFA: interpreting negative factor loadings [duplicate]

I've run an exploratory factor analysis with oblique rotation, and specifying three factors. The first two factors are correlated at almost zero with one another, while there's a negative correlation ...
0
votes
1answer
173 views

PCA scores in my own implementation have different sign from the ones computed in R [duplicate]

I am trying to implement PCA (NIPALS method) using Excel. The problem is that my results are not exactly matching with the results of R. There is only a difference in sign: if my scores are positive, ...
1
vote
0answers
116 views

How to reverse the sign of factor loadings in factor analysis? [duplicate]

I'm doing a factor analysis and using the resulting factors in a regression. I'm using SAS. A number of the variables load positively on a factor. In order to make it easier to interpret in the final ...
0
votes
0answers
107 views

Does it mean anything when all items load negatively on one factor? [duplicate]

note: A few people have marked this question as duplicate - But my question here is not answered in the other question. Though a fine distinction, what I was asking about here was not whether the ...
0
votes
1answer
61 views

What does it mean to have a high/low value for a sample in the 1st principal component? [duplicate]

I applied PCA on an $n\times p$ matrix where $n$ means the number of samples and $p$ means the number of variables, and I am using the 1st principal component (PC) as the new representation of the ...
1
vote
0answers
70 views

Getting PCA eigenvectors with the values of opposite sign [duplicate]

I am performing a PCA analysis in Matlab on a $110\times 7$ dataset using some custom code. I am checking my code against Matlab's princomp and my eigenvectors are ...
0
votes
0answers
50 views

Principal Component Analysis [duplicate]

I am doing PCA using Matlab's pca() function and R's prcomp() function. They give identical principal components in some cases and same values and opposite sign in some other cases. Why is this ...
1
vote
0answers
43 views

Eigenvectors computed by Matlab's princomp() and eig() have different signs [duplicate]

I am trying to write a PCA function in MATLAB. I know that there is the function princomp, I just wanted to understand the process for myself. One problem I've ...
0
votes
0answers
25 views

Computing eigenvectors for PCA: what to do about the freedom to choose the sign? [duplicate]

After an eigenvector computation for PCA, I get the eigenvector $(a, b)$ where $a=b$. This means that if I choose $a=1$, then also $b$ would be equal to $1$, and if I choose $a=2$, $b$ would also be ...
1
vote
0answers
24 views

Is it reasonable to get PC component score in the inverse direction to the original data? [duplicate]

I am using PCA in R to analyze groundwater level changes. I used: ...

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