Here's one way. # create matrices x and y with some sites in common x <- matrix(1, 4, 2) ; rownames(x) <- letters[1:4] y <- matrix(1, 4, 2) ; rownames(y) <- letters[3:6]
# identify which sites are in common for x and y xcommon <- rownames(x) %in% rownames(y) ycommon <- rownames(y) %in% rownames(x) # create new x and y matrices with only sites shared x2 <- x[xcommon, ] y2 <- y[ycommon, ] Cheers Etienne 2011/3/17 Scott Chamberlain <scttchamberla...@gmail.com> > If your datasets are dataframes (or you could convet matrices to > dataframes), you can use > > merge(x, y, by = "site") > > if y sites are a subset of x that will work, but if there are some sites in > y that are not in x, then I think you would write > > merge(x, y, by = "site", all = TRUE) > > which will keep sites in y that are not in x, then you could just delete > sites not in x but in y > > On Thursday, March 17, 2011 at 8:17 AM, Andres Mellado Diaz wrote: > > > > > > Dear list members, > > > > I have two data sets (sites by species) with some sites in common, one > with invertebrate data (X) and one with diatoms data (Y). I would like to > get both new Xc and Yc matrices showing only those sites common to X and Y, > to make similarity matrices and perform a mantel test. Hope you can help me > with this, > > > > Many thanks in advance, > > > > Andrés > > > > Dr. Andrés Mellado Díaz > > > > Center for Hydrological Studies CEH-CEDEX > > Water Quality Department > > Pº bajo de la Virgen del Puerto, 3 > > 28005, Madrid > > SPAIN > > [[alternative HTML version deleted]] > > _______________________________________________ > > R-sig-ecology mailing list > > R-sig-ecology@r-project.org > > https://stat.ethz.ch/mailman/listinfo/r-sig-ecology > > > > [[alternative HTML version deleted]] > > > _______________________________________________ > R-sig-ecology mailing list > R-sig-ecology@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-ecology > > [[alternative HTML version deleted]]
_______________________________________________ R-sig-ecology mailing list R-sig-ecology@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-ecology
