On 30-Sep-03 Rajarshi Guha wrote: > Hi, > I'm trying to take a set of rows and columns out of a matrix. I hve > been using the index aray approach. My overll matrix is X and is 179 x > 65. I want to take out 4 columns and 161 rows. > > Thus I made a 161 x 2 array I and filled it up with the row,col > indices. > However doing, > > X[ I ] gives me a vector of the extracted elements. Is there anyway I > can coerce this into a 161 x 4 matrix?
X[c(list_of_rows),c(list_of_cols)] should do it. E.g. X[c(2,5,7,9),c(3,5,6)] Alternatively you can make index vectors iR (for rows), iC (for cols) which have values TRUE for what you want to select and FALSE for the rest; then X[iR,iC] will also do it. There are other approaches -- you should choose whichever most closely fits in with your criteria for row and column selection. E.g. X[iR,c(3,5,6)] would also do! What it all boils down to is an expression of the form X[rowselector, colselector] Hope this helps, Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <[EMAIL PROTECTED]> Fax-to-email: +44 (0)870 167 1972 Date: 30-Sep-03 Time: 19:48:09 ------------------------------ XFMail ------------------------------ ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help