Sorry, I don't think I made myself clear enough with my initial query! I am wishing to investigate the temporal evolution of the pca: if we assume that every 50 rows of my data frame is representitive of, for instance, 1 day of data, I am hoping to automate a process whereby a pca is performed on every 50 rows of data and the loading for PC1 and PC2 for each variable (i.e. each column) is represented as a point on a plot - so a years' data will be represented as two lines (representing PC1 and PC2) on a time series plot for each variable.
Laura Quinn Institute of Atmospheric Science School of Earth and Environment University of Leeds Leeds LS2 9JT tel: +44 113 343 1596 fax: +44 113 343 6716 mail: [EMAIL PROTECTED] On Mon, 16 May 2005, Gavin Simpson wrote: > Laura Quinn wrote: > > Please could someone point me in the right direction as I appear to be > > having a total mental block with fairly basic PCA problem! > > > > I have a large dataframe where rows represent independent > > observations and columns are variables. I am wanting to perform PCA > > sequentially on blocks of nrows at a time and produce a graphical output > > of the loadings for the first 2 EOFs for each variable. > > > > I'm sure I've performed a very similar routine in the past, but the method > > is currently escaping me. > > > > Any help gratefully received! > > Hi Laura, > > data(iris) > iris.dat <- iris[,1:4] > pca.1 <- prcomp(iris.dat[1:50, ], scale = TRUE) > pca.2 <- prcomp(iris.dat[51:100, ], scale = TRUE) > pca.3 <- prcomp(iris.dat[100:150, ], scale = TRUE) > > biplot(pca.1) > etc... > > There is a better way of subsetting this data set as the 5th col of iris > is a factor and we could use the subset argument to prcomp to do the > subsetting without having to know that there are 50 rows per species. > Take a look at that argument if you have a variable that defines the > blocks for you. > > Is this what you were after? > > All the best, > > Gav > -- > %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% > Gavin Simpson [T] +44 (0)20 7679 5522 > ENSIS Research Fellow [F] +44 (0)20 7679 7565 > ENSIS Ltd. & ECRC [E] gavin.simpsonATNOSPAMucl.ac.uk > UCL Department of Geography [W] http://www.ucl.ac.uk/~ucfagls/cv/ > 26 Bedford Way [W] http://www.ucl.ac.uk/~ucfagls/ > London. WC1H 0AP. > %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% > ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html