Help with PCA
Sarah and elisacarli21 principal in the psych package will do principal components of a correlation or covariance matrix. ex: library(psych) principal(Thurstone,3,rotate="none") #First three principal components of the Thurstone correlation matrix #compare with eigen e <- eigen(Thurstone) #perform an eigen value decomposition e #show the resuls e$vectors %*% diag(sqrt(e$values)) #convert to "loadings" and compare with the output from principal Bill
On Dec 28, 2011, at 9:09 AM, Sarah Goslee wrote:
Hi, On Wed, Dec 28, 2011 at 7:54 AM, elisacarli21 <elisacarli21 at gmail.com> wrote:
Dear all, I've a correlation matrix with rows and columns headings. I've two questions: 1) How can i import it in R, setting first row as row heading and first column as column heading?
read.table, with the appropriate options. You can see what they are by typing ?read.table at an R prompt.
2) Which is the best principal component anlysis package in R?
Best for what? I'd start with ?princomp and if that doesn't meet your needs go looking farther. www.rseek.org is good for finding R functions for particular purposes. But if you're starting with the correlation matrix rather than the raw data, you might need to do the eigenanalysis yourself rather than relying on an existing function that assumes raw data. Sarah -- Sarah Goslee http://www.functionaldiversity.org
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