Hi, Here are two different ways to create a 0 x 0 logical matrix:
m1 <- matrix(nrow=0, ncol=0) m1 # <0 x 0 matrix> m2 <- as.matrix(data.frame()) m2 # <0 x 0 matrix> Surprisingly: identical(m1, m2) # [1] FALSE That's because of their dimnames: dimnames(m1) # NULL dimnames(m2) # [[1]] # NULL # # [[2]] # NULL More generally this can be observed with 0-col matrices: m1 <- matrix(nrow=5, ncol=0) m2 <- as.matrix(data.frame(stuff=11:15)[0]) identical(m1, m2) # FALSE The culprit is this line in as.matrix.data.frame(): dimnames(X) <- list(dn[[1L]], unlist(collabs, use.names = FALSE)) Shouldn't as.matrix.data.frame() collapse the list of NULLs into a NULL before setting the dimnames? Alternatively, maybe a more general solution could be to have the dimnames() setter take care of this. There seems to be a lot of code around that is potentially setting a list of NULLs as the dimnames of an object, so having dimnames<- do the collapse would fix the problem in one place once for all and avoid a lot of repeated code. Finally, having this functionality available at the C level would be great. Would basically be a wrapper to Rf_setAttrib(x, R_DimNamesSymbol, dimnames) that takes care of the collapse. The SET_DIMNAMES macro could be redefined to call that wrapper instead... Thanks, H. -- Hervé Pagès Program in Computational Biology Division of Public Health Sciences Fred Hutchinson Cancer Research Center 1100 Fairview Ave. N, M1-B514 P.O. Box 19024 Seattle, WA 98109-1024 E-mail: hpa...@fredhutch.org Phone: (206) 667-5791 Fax: (206) 667-1319 ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
