[R] Finding combination of states

[Eric Berger]

My initial response was buggy and also used a deprecated function.
Also, it seems possible that one may want to rule out any strings where the
same state appears consecutively.
I say that such a string has a repeat.

myExpand <- function(v, n) {
  do.call(tidyr::expand_grid, replicate(n, v, simplify = FALSE))
}

no_repeat <- function(s) {
  v <- unlist(strsplit(s, NULL))
  sum(v[-1]==v[-length(v)]) == 0
}

f <- function(states, nsteps, first, last, rm_repeat=TRUE) {
  if (nsteps < 3) stop("nsteps must be at least 3")
    out <- paste(first,
          myExpand(states, nsteps-2) |>
            apply(MAR=1, \(x) paste(x, collapse="")),
          last, sep="")
    if (rm_repeat) {
      ok <- sapply(out, no_repeat)
      out <- out[ok]
    }
    out
}

f(LETTERS[1:5],4,"B","E")

#  [1] "BABE" "BACE" "BADE" "BCAE" "BCBE" "BCDE" "BDAE" "BDBE" "BDCE"
"BEAE" "BEBE" "BECE" "BEDE"

On Mon, Sep 4, 2023 at 10:33 PM Bert Gunter <bgunter.4567 using gmail.com> wrote:

> Sorry, my last line should have read:
>
> If neither this nor any of the other suggestions is what is desired, I
> think the OP will have to clarify his query.
>
> Bert
>
> On Mon, Sep 4, 2023 at 12:31 PM Bert Gunter <bgunter.4567 using gmail.com>
> wrote:
>
>> I think there may be some uncertainty here about what the OP requested.
>> My interpretation is:
>>
>> n different times
>> k different states
>> Any state can appear at any time in the vector of times and can be
>> repeated
>> Initial and final states are given
>>
>> So modifying Tim's expand.grid() solution a bit yields:
>>
>> g <- function(ntimes, states, init, final){
>>    ## ntimes: integer, number of unique times
>>    ## states: vector of unique states
>>    ## init: initial state
>>    ## final: final state
>> do.call(paste0,c(init,expand.grid(rep(list(states), ntimes-2)), final))
>> }
>>
>> e.g.
>>
>> > g(4, LETTERS[1:5], "B", "D")
>>  [1] "BAAD" "BBAD" "BCAD" "BDAD" "BEAD" "BABD" "BBBD" "BCBD"
>>  [9] "BDBD" "BEBD" "BACD" "BBCD" "BCCD" "BDCD" "BECD" "BADD"
>> [17] "BBDD" "BCDD" "BDDD" "BEDD" "BAED" "BBED" "BCED" "BDED"
>> [25] "BEED"
>>
>> If neither this nor any of the other suggestions is not what is desired,
>> I think the OP will have to clarify his query.
>>
>> Cheers,
>> Bert
>>
>> On Mon, Sep 4, 2023 at 9:25 AM Ebert,Timothy Aaron <tebert using ufl.edu>
>> wrote:
>>
>>> Does this work for you?
>>>
>>> t0<-t1<-t2<-LETTERS[1:5]
>>> al2<-expand.grid(t0, t1, t2)
>>> al3<-paste(al2$Var1, al2$Var2, al2$Var3)
>>> al4 <- gsub(" ", "", al3)
>>> head(al3)
>>>
>>> Tim
>>>
>>> -----Original Message-----
>>> From: R-help <r-help-bounces using r-project.org> On Behalf Of Eric Berger
>>> Sent: Monday, September 4, 2023 10:17 AM
>>> To: Christofer Bogaso <bogaso.christofer using gmail.com>
>>> Cc: r-help <r-help using r-project.org>
>>> Subject: Re: [R] Finding combination of states
>>>
>>> [External Email]
>>>
>>> The function purrr::cross() can help you with this. For example:
>>>
>>> f <- function(states, nsteps, first, last) {
>>>    paste(first, unlist(lapply(purrr::cross(rep(list(v),nsteps-2)),
>>> \(x) paste(unlist(x), collapse=""))), last, sep="") } f(LETTERS[1:5], 3,
>>> "B", "E") [1] "BAE" "BBE" "BCE" "BDE" "BEE"
>>>
>>> HTH,
>>> Eric
>>>
>>>
>>> On Mon, Sep 4, 2023 at 3:42 PM Christofer Bogaso <
>>> bogaso.christofer using gmail.com> wrote:
>>> >
>>> > Let say I have 3 time points.as T0, T1, and T2.(number of such time
>>> > points can be arbitrary) In each time point, an object can be any of 5
>>> > states, A, B, C, D, E (number of such states can be arbitrary)
>>> >
>>> > I need to find all possible ways, how that object starting with state
>>> > B (say) at time T0, can be on state E (example) in time T2
>>> >
>>> > For example one possibility is BAE etc.
>>> >
>>> > Is there any function available with R, that can give me a vector of
>>> > such possibilities for arbitrary number of states, time, and for a
>>> > given initial and final (desired) states?
>>> >
>>> > ANy pointer will be very appreciated.
>>> >
>>> > Thanks for your time.
>>> >
>>> > ______________________________________________
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>>> ______________________________________________
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>>> 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 using 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.
>>>
>>

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