Hi fellow R-users,
I have run into a problem when trying to identify the number of rows in a
matrix. Say we have an arbitrary 5 by 5 matrix called temp:
temp <- matrix(norm(25), nrow=5)
The problem is that nrow(temp[1,]) returns NULL. I would like it to return 1
because in my larger program I am indexing the rows of large matrices according
to another variable and I need to test when the resulting matrices have 0, 1 or
more rows.
Thanks in advance for any assistance.
Best regards,
Gregory Gentlemen
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nrow is for number of rows in matrix/data.frame, here you can use: NROW(temp[1,]) length(temp[1,]) But if you want the index of row try this: unique(row(temp)[1,]) On 14/03/2008, Gregory Gentlemen <gregory_gentlemen at yahoo.ca> wrote:> Hi fellow R-users, > > I have run into a problem when trying to identify the number of rows in a matrix. Say we have an arbitrary 5 by 5 matrix called temp: > > temp <- matrix(norm(25), nrow=5) > > The problem is that nrow(temp[1,]) returns NULL. I would like it to return 1 because in my larger program I am indexing the rows of large matrices according to another variable and I need to test when the resulting matrices have 0, 1 or more rows. > > Thanks in advance for any assistance. > > Best regards, > Gregory Gentlemen > > > > > --------------------------------- > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at 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. >-- Henrique Dallazuanna Curitiba-Paran?-Brasil 25? 25' 40" S 49? 16' 22" O
Try temp[1,,drop=FALSE] See ?"[" for the explanation. Gabor On Fri, Mar 14, 2008 at 04:46:10PM -0400, Gregory Gentlemen wrote:> Hi fellow R-users, > > I have run into a problem when trying to identify the number of rows in a matrix. Say we have an arbitrary 5 by 5 matrix called temp: > > temp <- matrix(norm(25), nrow=5) > > The problem is that nrow(temp[1,]) returns NULL. I would like it to return 1 because in my larger program I am indexing the rows of large matrices according to another variable and I need to test when the resulting matrices have 0, 1 or more rows. > > Thanks in advance for any assistance. > > Best regards, > Gregory Gentlemen > > > > > --------------------------------- > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at 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.-- Csardi Gabor <csardi at rmki.kfki.hu> UNIL DGM