I don't see how you are getting the result you provide.
> m
[,1] [,2] [,3] [,4] [,5]
[1,] 0 0 0 0 0
[2,] 0 0 0 0 0
[3,] 0 0 0 0 0
[4,] 1 2 3 0 0
[5,] 1 2 3 0 0
[6,] 1 2 3 0 0
[7,] 1 2 3 0 0
[8,] 1 2 3 0 0
[9,] 1 2 3 4 0
[10,] 1 2 3 4 0
[11,] 1 2 3 4 5
[12,] 1 2 3 4 5
> t(sapply(1:8, function(x) diag(m[x:12, ])))
[,1] [,2] [,3] [,4] [,5]
[1,] 0 0 0 0 0
[2,] 0 0 3 0 0
[3,] 0 2 3 0 0
[4,] 1 2 3 0 0
[5,] 1 2 3 0 0
[6,] 1 2 3 4 0
[7,] 1 2 3 4 5
[8,] 1 2 3 4 5
These are all of the diagonals from the 1st through 8th rows. The first 3 begin
with 0 so we leave them out, but then we have 4th: 1, 2, 3; 5th: 1, 2, 3; 6th:
1, 2, 3, 4, etc so you must have some additional rule in mind to get your
answer.
-------------------------------------
David L Carlson
Department of Anthropology
Texas A&M University
College Station, TX 77840-4352
-----Original Message-----
From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Jorge I Velez
Sent: Tuesday, October 27, 2015 2:44 PM
To: jim holtman
Cc: R-help
Subject: Re: [R] Extract entries from matrix
Dear Jim,
Thank you very much for your quick reply.
I am sorry for the confusion it may have caused, but I messed up the
indexes in my example. I would like, from the following matrix "m"
## input
m <- structure(c(0L, 0L, 0L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 0L,
0L, 0L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 0L, 0L, 0L, 3L, 3L,
3L, 3L, 3L, 3L, 3L, 3L, 3L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 4L,
4L, 4L, 4L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 5L, 5L), .Dim = c(12L,
5L))
to obtain
1 2 3 1 2 3 4 5 1
Sure using m[idx] will give the desired result. The problem is that idx is
not known and needs to be determined from "m". I would like to use
something like
extractDiagonals(m)
## [1] 1 2 3 1 2 3 4 5 1
I look forward to your reply. Thanks in advance.
Best regards,
Jorge Velez.-
On Tue, Oct 27, 2015 at 2:31 PM, jim holtman <jholt...@gmail.com> wrote:
> If you want to use the numbers you gave a the index into the matrix, then
> you can create a matrix with the values and then index into 'm'. I don't
> see a '4' in the output example you gave using your index values:
>
> > m <- structure(c(0L, 0L, 0L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
> + 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 0L, 0L, 0L, 2L, 2L, 2L, 2L,
> + 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 0L,
> + 0L, 0L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L,
> + 3L, 3L, 3L, 3L, 3L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 4L, 4L, 4L,
> + 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 0L, 0L, 0L, 0L, 0L,
> + 0L, 0L, 0L, 0L, 0L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L,
> + 5L), .Dim = c(22L, 5L))
> > # create index matrix
> > indx <- matrix(c(4, 1,
> + 5, 2,
> + 6, 3,
> + 7, 1,
> + 8, 2,
> + 9, 3,
> + 10, 1,
> + 11, 2,
> + 12, 3), ncol = 2, byrow = TRUE)
> >
> >
> > m
> [,1] [,2] [,3] [,4] [,5]
> [1,] 0 0 0 0 0
> [2,] 0 0 0 0 0
> [3,] 0 0 0 0 0
> [4,] 1 2 3 0 0
> [5,] 1 2 3 0 0
> [6,] 1 2 3 0 0
> [7,] 1 2 3 0 0
> [8,] 1 2 3 0 0
> [9,] 1 2 3 4 0
> [10,] 1 2 3 4 0
> [11,] 1 2 3 4 5
> [12,] 1 2 3 4 5
> [13,] 1 2 3 4 5
> [14,] 1 2 3 4 5
> [15,] 1 2 3 4 5
> [16,] 1 2 3 4 5
> [17,] 1 2 3 4 5
> [18,] 1 2 3 4 5
> [19,] 1 2 3 4 5
> [20,] 1 2 3 4 5
> [21,] 1 2 3 4 5
> [22,] 1 2 3 4 5
> > indx
> [,1] [,2]
> [1,] 4 1
> [2,] 5 2
> [3,] 6 3
> [4,] 7 1
> [5,] 8 2
> [6,] 9 3
> [7,] 10 1
> [8,] 11 2
> [9,] 12 3
> > m[indx]
> [1] 1 2 3 1 2 3 1 2 3
>
>
> Jim Holtman
> Data Munger Guru
>
> What is the problem that you are trying to solve?
> Tell me what you want to do, not how you want to do it.
>
> On Tue, Oct 27, 2015 at 2:43 PM, Jorge I Velez <jorgeivanve...@gmail.com>
> wrote:
>
>> Dear R-help,
>>
>> I am working with a matrix "m" from which I would like to extract some
>> elements. An toy example is as follows:
>>
>> ## input matrix
>> m <- structure(c(0L, 0L, 0L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
>> 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 0L, 0L, 0L, 2L, 2L, 2L, 2L,
>> 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 0L,
>> 0L, 0L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L,
>> 3L, 3L, 3L, 3L, 3L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 4L, 4L, 4L,
>> 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 0L, 0L, 0L, 0L, 0L,
>> 0L, 0L, 0L, 0L, 0L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L,
>> 5L), .Dim = c(22L, 5L))
>>
>> R> m
>> # [,1] [,2] [,3] [,4] [,5]
>> # [1,] 0 0 0 0 0
>> # [2,] 0 0 0 0 0
>> # [3,] 0 0 0 0 0
>> # [4,] 1 2 3 0 0
>> # [5,] 1 2 3 0 0
>> # [6,] 1 2 3 0 0
>> # [7,] 1 2 3 0 0
>> # [8,] 1 2 3 0 0
>> # [9,] 1 2 3 4 0
>> # [10,] 1 2 3 4 0
>> # [11,] 1 2 3 4 5
>> # [12,] 1 2 3 4 5
>>
>> >From "m", I would like to extract the entries
>>
>> 4, 1
>> 5, 2
>> 6, 3
>> 7, 1
>> 8, 2
>> 9, 3
>> 10, 1
>> 11, 2
>> 12, 3
>>
>> so at the end of applying a function "f" to "m" I get
>>
>> 1, 2, 3, 1, 2, 3, 4, 1, 2, 3
>>
>>
>> Basically the idea is to extract the diagonal elements until a zero is
>> found.
>>
>> In the real problem the dimensions of "m" are much bigger, but this
>> smaller
>> version of "m" illustrate what needs to be done.
>>
>> I would greatly appreciate any ideas on how to do this.
>>
>> Thanks in advance,
>> Jorge Velez.-
>>
>> [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> 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.
>>
>
>
[[alternative HTML version deleted]]
______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
______________________________________________
R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
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.
