Re: [R] extract a subset of non-contiguous elements of a matrix

2014-06-20 Thread PIKAL Petr
Hi You can pad some NA to the result before transforming it to required matrix but as Frede pointed out, what do you want to do with such result? tm.1=rbind(c(1,-3,2,-4), c(1,-3,2,-4),c(1,-3,2,-4)) xx-which(tm.1 0, arr.ind=TRUE) res-apply(xx, 1, paste0, collapse=,) dim(res)-c(3,2) res

[R] extract a subset of non-contiguous elements of a matrix

2014-06-19 Thread carol white
Hi, Is there a way to extract a subset of non-contiguous elements of a matrix elegantly and with 1 or very few scripts? Suppose I have a matrix of positive and negative numbers (m) and I want to retrieve only the positive number. This I can do which(m0, arr.ind=T) which gives the indices of

Re: [R] extract a subset of non-contiguous elements of a matrix

2014-06-19 Thread Bart Kastermans
On 19 Jun 2014, at 13:19, carol white wht_...@yahoo.com wrote: Hi, Is there a way to extract a subset of non-contiguous elements of a matrix elegantly and with 1 or very few scripts? Suppose I have a matrix of positive and negative numbers (m) and I want to retrieve only the positive

Re: [R] extract a subset of non-contiguous elements of a matrix

2014-06-19 Thread carol white
The extracted values don't form a matrix and that's the question how to extract because which returns the indexes? that is, from 1,1 2,1 1,2 how to retrieve values? Or if at the position 2,1, there is a negative value, how to retrieve 1,1 1,2 Carol On Thursday, June 19, 2014 1:29 PM, Bart

Re: [R] extract a subset of non-contiguous elements of a matrix

2014-06-19 Thread peter dalgaard
This _was_ in the answer you got, but to clarify things, perhaps try this: (M - matrix(1:9,3,3)) (ix - rbind(c(3,2),c(1,3))) M[3,2] M[1,3] M[ix] -pd On 19 Jun 2014, at 14:12 , carol white wht_...@yahoo.com wrote: The extracted values don't form a matrix and that's the question how to

Re: [R] extract a subset of non-contiguous elements of a matrix

2014-06-19 Thread Bart Kastermans
If you give an example of input and desired output I can think about this. But at this point I do not understand what you want. In the example I gave the positive elements do not form a submatrix in any way I can think of. On 19 Jun 2014, at 15:04, carol white wht_...@yahoo.com wrote: well

Re: [R] extract a subset of non-contiguous elements of a matrix

2014-06-19 Thread carol white
 tm.1=rbind(c(1,-3,2,-4), c(1,-3,2,-4),c(1,-3,2,-4)) which(tm.1 0, arr.ind=TRUE)      row col [1,]   1   1 [2,]   2   1 [3,]   3   1 [4,]   1   3 [5,]   2   3 [6,]   3   3 so the answer should have the elements of tm.1 with the following indexes 1,1 1,3 2,1 2,3

Re: [R] extract a subset of non-contiguous elements of a matrix

2014-06-19 Thread Bart Kastermans
On 19 Jun 2014, at 15:16, carol white wht_...@yahoo.com wrote: tm.1=rbind(c(1,-3,2,-4), c(1,-3,2,-4),c(1,-3,2,-4)) which(tm.1 0, arr.ind=TRUE) row col [1,] 1 1 [2,] 2 1 [3,] 3 1 [4,] 1 3 [5,] 2 3 [6,] 3 3 so the answer should have the elements of

Re: [R] extract a subset of non-contiguous elements of a matrix

2014-06-19 Thread Frede Aakmann Tøgersen
As Peter and Bart I really have a problem understanding you. Perhaps if you tell us what your desired result is going to used for we can be more helpful. You can do that using your latest example. In that example you want a matrix of sets of row and column indices. This will probably have to

Re: [R] extract a subset of non-contiguous elements of a matrix

2014-06-19 Thread carol white
I realize that that the problem arises if there is a different number of negative numbers in the rows and columns of the original matrix. In this case, the resulting matrix won't have the same number of rows for all columns. The problem for ex doesn't arise for my example but for Bart's example

Re: [R] extract a subset of non-contiguous elements of a matrix

2014-06-19 Thread Frede Aakmann Tøgersen
You are really not helpful here. Are we talking the same scientific language? Br. Frede Sendt fra Samsung mobil Oprindelig meddelelse Fra: carol white Dato:19/06/2014 15.46 (GMT+01:00) Til: Frede Aakmann Tøgersen ,Bart Kastermans Cc: r-help@r-project.org Emne: Re: [R]