# pca

1. ### Principle Components Analysis: Variation

Why do you choose the two factors with the highest proportion of variance to use in an analysis? Wouldn't a higher proportion of variance imply less correlation?
2. ### PCA and symmetric distribution.

Hello, I hope you can clarify my doubts. I'm an Italian student of business administration. For my thesis I study the application of PCA method for the reduction of the original variables, and my data have skewed distribution. I have read that the PCA works better when the original data have...
3. ### PCA using Statistica

While trying to do PCA using Statistica, I am receiving the following error message: The percentage of valid cases (65.67%) for variable files is less than the required minimum percentage of valid cases (80.00%). The analysis stops. How to solve this issue? I have 40 variables which I...
4. ### Factor Analysis: Creating Reliable Scales

Hello all. I have a question I hope someone can help me with. I items which I have run PCA on and come up with 8 factors from about 20 vairables. I want to create a index to compare responses based on a classic political economic scale. i.e., some variables load heavily on items related to...
5. ### PCR interaction of PCs

Hi, I am using PCA to avoid multicollinearity problems and then I want to use the first 2 PCs in linear regression. The 1st PC contains 60% of variability and the 2nd 32%. Is it valid if I use a data step in SAS, create a new variable which is the interaction of these 2 PCs and say that...
6. ### Between-Group and Within-Group PCA

Hi all, I'm running a PCA with two species (one fossil and one extant) divided into multiple geographic groups. The program I'm using is called PAST (PAlaeontological STatistics). Anyhow, I'm a little confused about within-group and between-group PCAs and how they differ from a PCA...
7. ### Can I transform the principal components...?

Hi all. I am using PCA to generate PCs and then using them as independent variables in regression. I added an extra data-step after PCA which is transformation of the PCs e.g. X=prin1^2 This significantly improved the subsequent regression model, however I am not sure if transforming the...
8. ### Three-way PCA

Hi all, Does anybody have experience with 3-way PCA? Is there any example using SAS? I am not sure if I understand how it is different from the classical PCA... Thank you
9. ### Correlation test for PCA

Hello, I have done two independent PCA (Principal component analysis) with two different datasets in R. I have made interpolated geographic maps with the first PC which show the same pattern for both analysis but the comparison solely based on the maps is not enough for me. I want to do a...
10. ### PCA - To check

Hi I got a data set and tried my hand in doing PCA using SPSS and for the same set of data carried out PCA by using matlab program (first standardising data and then using princomp). I have got the PC1 Vs PC2 Vs PC3 plot to be different in both the cases. Can some one tell me which is...
11. ### PCA on time series

Hi, excuse my poor english... I need to reduce number of indicators (and to perform a PCA) on dataset: year ind(1) ind(2) ... ind(n) 2000 x(1,1) x(1,2) ... x(1,n) ..... 2010 x(11,1) x(11,2) ... x(11,n) x(i,j) are quantitative values about indicators like production, resources, ecc. How...
12. ### What can of analysis to use - Correlation between drivers and forest carbon storage

Hey, I am new to this forum and would like to say thanks in advance to anyone who replies to this message. I have tried thoroughly to discover the solution myself over the last couple of days and have become confused. I have been trying to discover what kind of statistical technique I should...
13. ### PCA on forest carbon production

Hey, I am new to this forum and would like to say thanks in advance to anyone who replies to this message. I have tried thoroughly to discover the solution myself over the last couple of days and have become confused. :confused: (edit: think this post may be in the wrong section of the site if...
14. ### [Primer-E] Behaviours- PCA then ANOVA on factor scores, or PERMANOVA on original data

Hello, I am hoping someone could give me some advice on an approach to analysing my data. I have a set of behavioural data (39 behavioural variables such as time spent foraging, number of foraging bouts, time spent vigilant etc), which were measured for 34 sites over 3 nights. Each of the 34...
15. ### [Primer-E] PCA - no option for varimax rotation?

Hi, I am trying to figure out how to run a PCA on some behavioural data in Primer-E. Just a little confused as in the manual there is no reference to choosing a type of rotation, which I understand is usually Varimax. Am I missing something, or does Primer simply not use rotation...
16. ### Why data standardization is necessary in Prinicple Component Analysis (PCA) ?

Dear Guys, Hi. Generally the PCA process is described as follows: 1: Get some data 2: Standardize the data 3: Calculate the covariance matrix 4: Calculate the eigenvectors and eigenvalues of the covariance matrix 5: Choosing components and forming a feature vector 6: Deriving the new...
17. ### Help on Semantic Differential, PCA - Input values?

Dear all, I am not good in statistics and I would be grateful if you could help me. I conducted a study on the perception of 50 different sounds and used the semantic differential technique to measure the response of subjects. The scale used was a double sided 5-point scale. (Example...