Hi, I'm working with a big square matrix (15k x 15k) and I have some trouble. I want to delete selecting rows and columns. I'm using something like this:> sel_r=c(15,34,384,985,4302,6213) > sel_c=c(3,151,324,3384,7985,14302) > matrix=matrix[-sel_r,-sel_c]but it works very slow. Does anybody know how to make it in faster way? Thank's -- View this message in context: http://www.nabble.com/delete-selecting-rows-and-columns-tf3308726.html#a9203533 Sent from the R help mailing list archive at Nabble.com.
I mean something like in MATLAB matrix(sel_r,:)=[] jastar wrote:> > Hi, > I'm working with a big square matrix (15k x 15k) and I have some trouble. > I want to delete selecting rows and columns. > I'm using something like this: > >> sel_r=c(15,34,384,985,4302,6213) >> sel_c=c(3,151,324,3384,7985,14302) >> matrix=matrix[-sel_r,-sel_c] > > but it works very slow. > Does anybody know how to make it in faster way? > Thank's >-- View this message in context: http://www.nabble.com/delete-selecting-rows-and-columns-tf3308726.html#a9327427 Sent from the R help mailing list archive at Nabble.com.
A one-dimensional delete might be faster:
n <- 4000
m <- 0.01
matr <- matrix(1:(n^2), n, n)
excl_r <- sample(n, m*n)
incl_r <- setdiff(1:n, excl_r)
excl_c <- sample(n, m*n)
incl_c <- setdiff(1:n, excl_c)
system.time(matr[-excl_r, -excl_c])
system.time(
{ m4 <- matr[outer(incl_r, incl_c, function(i, j) i + n*(j - 1)) ]
dim(m4) <- c(length(incl_r), length(incl_c))
} )
Heikki Kaskelma
jastar wrote:>
> Hi,
> I'm working with a big square matrix (15k x 15k) and I have
> some trouble.
> I want to delete selecting rows and columns.
> I'm using something like this:
>
>> sel_r=c(15,34,384,985,4302,6213)
>> sel_c=c(3,151,324,3384,7985,14302)
>> matrix=matrix[-sel_r,-sel_c]
>
> but it works very slow.
> Does anybody know how to make it in faster way?