I have an (n,m) matrix with rownames and colnames. The rownames are probe set ids. I know a value of one of the probe sets which is, say, in column 2 of the matrix. I would like to retrieve the rowname, or probe set id, of the row which contains this value. Neither of these work: matrix[,matrix[,2]==513.193057] (Error: (subscript) logical subscript too long) index <- which(matrix[,2] == 513.193057) matrix[index,] Of course, I could write.table() the matrix and search the file. But I would like to know how this is done in R/Bioconductor. Thank you very much. Juerg Straubhaar, Umass Med

>I have an (n,m) matrix with rownames and colnames. The rownames are probe set ids. I know a value of one of the probe sets which is, say, in column 2 of the matrix. I would like to retrieve the rowname, or probe set id, of the row which contains this value. > >Neither of these work: > >matrix[,matrix[,2]==513.193057] >(Error: (subscript) logical subscript too long) Try this: > tt <- matrix(1:20, ncol = 4) > tt [,1] [,2] [,3] [,4] [1,] 1 6 11 16 [2,] 2 7 12 17 [3,] 3 8 13 18 [4,] 4 9 14 19 [5,] 5 10 15 20 > tt[tt[,2] == 8, ] [1] 3 8 13 18 > >index <- which(matrix[,2] == 513.193057) >matrix[index,] > >Of course, I could write.table() the matrix and search the file. But I would like to know how this is done in R/Bioconductor. > >Thank you very much. > >Juerg Straubhaar, >Umass Med > >_______________________________________________ >Bioconductor mailing list >Bioconductor@stat.math.ethz.ch >https://www.stat.math.ethz.ch/mailman/listinfo/bioconductor Jianhua Zhang Department of Biostatistics Dana-Farber Cancer Institute 44 Binney Street Boston, MA 02115-6084

Hi, > matrix[,matrix[,2]==513.193057] > (Error: (subscript) logical subscript too long) matrix[,2]==513.193057 returns a logical vector the length of which is the number of rows of 'matrix'. Thus you would want to write matrix[matrix[,2]==513.193057, ] > index <- which(matrix[,2] == 513.193057) > matrix[index,] Note that all of the above may be problematic because of round-off errors, most likely this expression will not match for any row of 'matrix'. Please read the help pages on the == operator and the all.equal function (type: > help("==") > help(all.equal) Maybe matrix[abs(matrix[,2]-513.19 < 0.01), ] would be the simplest solution. Best wishes Wolfgang

Hi, for the record: Laurent pointed out a typo in my code example from the previous post - Please see below. Best wishes Wolfgang On Tue, 6 Jan 2004, Laurent Gautier wrote: > > Maybe > > matrix[abs(matrix[,2]-513.19 < 0.01), ] > > would be the simplest solution. > > Did you mean > matrix[abs(matrix[,2]-513.19) < 0.01, ] > ?