Edzer, say m is your matrix of TRUE's and FALSE's, then:
which(m,arr.ind=TRUE) will give you the column and row numbers of the matrix satisfying the conditions supplied to which. Hope it helps Caspar On Wed, Nov 17, 2010 at 8:29 PM, Edzer Pebesma <[email protected]> wrote: > List, > > given an arbitrary n x m boolean matrix, say > > [,1] [,2] [,3] [,4] [,5] > [1,] FALSE FALSE FALSE FALSE FALSE > [2,] FALSE FALSE TRUE FALSE FALSE > [3,] FALSE FALSE FALSE FALSE FALSE > [4,] FALSE FALSE FALSE TRUE TRUE > > I have the TRUE entries (indexes) of each column, in a list > > [[1]] > integer(0) > > [[2]] > integer(0) > > [[3]] > [1] 2 > > [[4]] > [1] 4 > > [[5]] > [1] 4 > > How can I, from this list, efficiently obtain the TRUE entries of each > row, in this case > > [[1]] > integer(0) > > [[2]] > [1] 3 > > [[3]] > integer(0) > > [[4]] > [1] 4 5 > > without constructing the n x m boolean matrix? > -- > Edzer Pebesma > Institute for Geoinformatics (ifgi), University of Münster > Weseler Straße 253, 48151 Münster, Germany. Phone: +49 251 > 8333081, Fax: +49 251 8339763 http://ifgi.uni-muenster.de > http://www.52north.org/geostatistics [email protected] > > _______________________________________________ > R-sig-Geo mailing list > [email protected] > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > _______________________________________________ R-sig-Geo mailing list [email protected] https://stat.ethz.ch/mailman/listinfo/r-sig-geo
