Hi David, Thanks for your help. This is exactly what I want. But, I have number of rows of my matrix = 25k and columns size as 80k. So, when I define a matrix object, it is throwing an error saying can not allocate a vector of length (25K * 80k). I heard that, this data can still be loaded into R using sparseMatrix. However, I couldn't get a syntax for creating the same. Could someone kindly help me in this regard.
Thanks Pallavi David Winsemius wrote: > > > On Oct 26, 2009, at 5:06 AM, Pallavi Palleti wrote: > >> >> Hi all, >> >> I am new to R and learning the same. I would like to create a sparse >> matrix >> from an existing file whose contents are in the format >> "rowIndex,columnIndex,value" >> >> for ex: >> 1,2,14 >> 2,4,15 >> >> I would like to create a sparse matrix by taking the above as input. >> However, I couldn't find an example where the data was being read >> from a >> file. I tried searching in R tutorial and also searched for the same >> in web >> but in vain. Could some one kindly help me how to give the above >> format as >> input in R to create a sparse matrix. > > ex <- read.table(textConnection("1,2,14 > 2,4,15") , sep=",") > ex > # V1 V2 V3 > #1 1 2 14 > #2 2 4 15 > > M <- Matrix(0, 20, 20) > > > M > #20 x 20 sparse Matrix of class "dsCMatrix" > > [1,] . . . . . . . . . . . . . . . . . . . . > [2,] . . . . . . . . . . . . . . . . . . . . > [3,] . . . . . . . . . . . . . . . . . . . . > snip > > for (i in 1:nrow(ex) ) { M[ex[i, 1], ex[i, 2] ] <- ex[i, 3] } > > > M > 20 x 20 sparse Matrix of class "dgCMatrix" > > [1,] . 14 . . . . . . . . . . . . . . . . . . > [2,] . . . 15 . . . . . . . . . . . . . . . . > [3,] . . . . . . . . . . . . . . . . . . . . > snip > > > -- > > David Winsemius, MD > Heritage Laboratories > West Hartford, CT > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > > -- View this message in context: http://www.nabble.com/Creating-a-sparse-matrix-from-a-file-tp26056334p26071964.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.