[R] listing a sequence of vectors in a matrix
Robin Hankin
r.hankin at noc.soton.ac.uk
Tue Aug 22 15:05:06 CEST 2006
Gabor makes a good point about seq() vs a:b [a common gotcha
for me].
I'll revise my original function to:
> f <- function(a,n){(seq(length=a))[1:n]}
> t(sapply(c(2,3,4,4,4,5,6,0),f,n=5))
[,1] [,2] [,3] [,4] [,5]
[1,] 1 2 NA NA NA
[2,] 1 2 3 NA NA
[3,] 1 2 3 4 NA
[4,] 1 2 3 4 NA
[5,] 1 2 3 4 NA
[6,] 1 2 3 4 5
[7,] 1 2 3 4 5
[8,] NA NA NA NA NA
>
rksh
On 22 Aug 2006, at 13:55, Gabor Grothendieck wrote:
> Here are two solutions. seq(length = ...) instead of
> just seq(...) is so that v can possibly contain zeros.
>
> # data
> v <- 3:5
>
> # solution 1 - rbind/lapply
> f <- function(n) {
> s = seq(length = n)
> replace(rep(NA, max(v)), s, s)
> }
> do.call(rbind, lapply(v, f))
>
> # solution 2 - loop
> mat <- matrix(NA, length(v), max(v))
> for(i in seq(v)) {
> s <- seq(length = v[i])
> mat[i, s] <- s
> }
>
>
> On 8/22/06, Sara-Jane Dunn <SND at bas.ac.uk> wrote:
>> Hi,
>>
>> I'm having trouble applying the matrix function. I'd like to be
>> able to
>> create a matrix of vectors filled in by rows, which are not all
>> the same
>> length, and so I need it to fill in NAs where applicable.
>>
>> It's easiest to explain with a simple example:
>>
>> Suppose vec = c(3,4,5). How can I form a matrix of the vectors
>> 1:vec[j]
>> for j=1:3?
>> i.e. 1 2 3 NA NA
>> 1 2 3 4 NA
>> 1 2 3 4 5
>> I've tried matrix(c(1:vec[j]),nrow=max(j),ncol=max(vec)) but it will
>> only give me a matrix with repeated values for j=1, like 1 2 3 1
>> 2
>> 3 1 2 3 1
>> 2 3 1 2 3
>>
>> Also using the list function hasn't got me anywhere either..
>>
>> Any help/ideas would be greatly appreciated!
>>
>> Many thanks,
>> Sara-Jane Dunn
>>
>> --
>> This message (and any attachments) is for the recipient only...
>> {{dropped}}
>>
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>>
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> 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.
--
Robin Hankin
Uncertainty Analyst
National Oceanography Centre, Southampton
European Way, Southampton SO14 3ZH, UK
tel 023-8059-7743
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