Your code does not produce the matrix in your image.
The first three rows contain all-zeros and the last row is missing.
The following line fixes that:
m <- rbind(m[-(1:3), ], 1:5)
Given that matrix, the following code produces the output
you have illustrated. It's so trivial however that I suspect
something must be missing in your problem description.
v <- numeric(nrow(m))
j <- 1
for (i in 1:nrow(m)) {
if (j > ncol(m) || m[i,j] == 0) {
j <- 1
}
v[i] <- m[i,j]
j <- j+1
}
v
Note that this puts 0 in the output if
there is a zero in your first column and
the "diagonal". Your example didn't have that.
B.
On Oct 28, 2015, at 1:17 PM, Jorge I Velez <jorgeivanve...@gmail.com> wrote:
> Dear all,
>
> I thought I would better send an image illustrating that the problem is
> (hope the file gets through). In the picture, the matrix "m" is given by
>
> ## input
> m <- structure(c(0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 2, 2,
> 2, 2, 2, 2, 2, 2, 2, 0, 0, 0, 3, 3, 3, 3, 3, 3, 3, 3, 3, 0, 0,
> 0, 0, 0, 0, 0, 0, 4, 4, 4, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 5,
> 5), .Dim = c(12L, 5L))
>
> We start from the entry [1,1] and select all values in the diagonal until
> we find the first zero. That is, we select the values in purple. Because
> the first zero is found in [4,4], the next matrix begins in the 4th row.
> The values of interest would be 1, 2, 3, 4, 5 (light blue). The last value
> in this resulting vector is entry m[8,5], which is located at the maximum
> number of columns of m. Hence, the next matrix to work with starts at row 9
> and the values of interest are 1, 2 (in orange).
>
> The output vector would then be of the same length as the number of rows in
> "m", and would contain the elements previously selected.
>
> Any ideas on how to proceed?
>
> Thank you very much in advance.
>
> Best regards,
> Jorge Velez.-
>
>
>
> On Tue, Oct 27, 2015 at 4:38 PM, Jorge I Velez <jorgeivanve...@gmail.com>
> wrote:
>
>> Thank you all for your solutions and comments.
>>
>> As Dr. Carlson mentioned, we leave rows 1 to 3 out as they are all zeroes.
>> Then, the entries I need to select from m are
>>
>> ----------------
>> entry value
>> ----------------
>> 4,1 ---> 1
>> 5,2 ---> 2
>> 6,3 ---> 3
>> 7,1 ---> 1
>> 8,2 ---> 2
>> 9,3 ---> 3
>> 10,4 ---> 4
>> 11,5 ---> 5
>> 12,1 ---> 1
>>
>> Note that the entry [7,4] is zero, so we start from the first column in
>> the 7th row and then select entry [7,1] instead. That's what I meant by
>> "...
>> the idea is to extract the diagonal elements until a zero is found." I
>> should have said *entries* instead of _diagonal elements_. I am sorry Dr.
>> Turner for the confusion.
>>
>> Starting with m
>>
>> 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
>>
>> the first submatrix to work with is
>>
>> # [4,] 1 2 3 0 0
>> # [5,] 1 2 3 0 0
>> # [6,] 1 2 3 0 0
>>
>> from which the elements of interest are 1, 2, 3. Note that the 7th row of
>> m is not included here because m[7, 5] = 0.
>>
>> Further, the second submatrix is
>>
>> # [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
>>
>> and the corresponding elements are 1, 2, 3, 4, 5.
>>
>> And the last matrix is
>>
>> #[12,] 1 2 3 4 5
>>
>> from which the position [12,1] is selected.
>>
>> So, the resulting entries from this process are 1, 2, 3, 1, 2, 3, 4, 5, 1.
>>
>> Thank you in advance for any additional insight you may provide.
>>
>> Regards,
>> Jorge Velez.-
>>
>>
>>
>> On Tue, Oct 27, 2015 at 4:06 PM, David L Carlson <dcarl...@tamu.edu>
>> wrote:
>>
>>> 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]]
>>>
>>> ______________________________________________
>>> 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.
>>>
>>
>>
> <example.png>______________________________________________
> 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.
______________________________________________
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.
