Hi On 5 Jan 2006 at 15:11, Chia, Yen Lin wrote:
Date sent: Thu, 5 Jan 2006 15:11:18 -0800 From: "Chia, Yen Lin" <[EMAIL PROTECTED]> To: <[email protected]> Subject: [R] convert matrix to data frame > Hi all, > > > > Suppose I have a 4 x 2 matrix A and I want to select the values in > second column such that the value in first column equals to k. > > > > I gave the colnames as alpha beta, so I was trying to access the info > using > > > > A$beta[A[,1]==k], however, I was told it's not a data frame, I can get > the object by using dollar sign. I tried data.frame(A), but it didn't > work. I believe its because matrix has a bit different structure from data.frame so its columns can not be simply called by names. But I wonder why data.frame(A) does not work for you? See below. > str(A) `data.frame': 4 obs. of 2 variables: $ alpha: num -1.181 -0.415 2.087 1.422 $ beta : num -0.0889 0.6828 -0.7035 -0.3351 > str(mat) num [1:4, 1:2] -1.1813 -0.4152 2.0865 1.4216 -0.0889 ... - attr(*, "dimnames")=List of 2 ..$ : chr [1:4] "1" "2" "3" "4" ..$ : chr [1:2] "alpha" "beta" > B<-data.frame(mat) > str(B) `data.frame': 4 obs. of 2 variables: $ alpha: num -1.181 -0.415 2.087 1.422 $ beta : num -0.0889 0.6828 -0.7035 -0.3351 > mat$alpha[mat[,1]<0] NULL > B$alpha[mat[,1]<0] [1] -1.181258 -0.415175 > > > > Any input on this will be very appreciated. Thanks. > > > > I tried looking in the manual, but I think I'm might be wrong about > the keywords. > > > > Yen Lin > > > [[alternative HTML version deleted]] > > ______________________________________________ > [email protected] mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! > http://www.R-project.org/posting-guide.html Petr Pikal [EMAIL PROTECTED] ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
