# [R] Finding combination of states

Bert Gunter bgunter@4567 @end|ng |rom gm@||@com
Tue Sep 5 02:08:17 CEST 2023

```... and just for fun, here is a non-string version (more appropriate for
complex state labels??):

gvec <- function(ntimes, states, init, final, repeats = TRUE)
## ntimes: integer, number of unique times
## states: vector of unique states
## init: initial state
## final: final state
{
out <- cbind(init,
as.matrix(expand.grid(rep(list(states),ntimes -2 ))),final)
if(!repeats)
out[ apply(out,1,\(x)all(x[-1] != x[-ntimes])), ]
else out
}

yielding:

> gvec(4, letters[1:5], "b", "e", repeats = TRUE)
init Var1 Var2 final
[1,] "b"  "a"  "a"  "e"
[2,] "b"  "b"  "a"  "e"
[3,] "b"  "c"  "a"  "e"
[4,] "b"  "d"  "a"  "e"
[5,] "b"  "e"  "a"  "e"
[6,] "b"  "a"  "b"  "e"
[7,] "b"  "b"  "b"  "e"
[8,] "b"  "c"  "b"  "e"
[9,] "b"  "d"  "b"  "e"
[10,] "b"  "e"  "b"  "e"
[11,] "b"  "a"  "c"  "e"
[12,] "b"  "b"  "c"  "e"
[13,] "b"  "c"  "c"  "e"
[14,] "b"  "d"  "c"  "e"
[15,] "b"  "e"  "c"  "e"
[16,] "b"  "a"  "d"  "e"
[17,] "b"  "b"  "d"  "e"
[18,] "b"  "c"  "d"  "e"
[19,] "b"  "d"  "d"  "e"
[20,] "b"  "e"  "d"  "e"
[21,] "b"  "a"  "e"  "e"
[22,] "b"  "b"  "e"  "e"
[23,] "b"  "c"  "e"  "e"
[24,] "b"  "d"  "e"  "e"
[25,] "b"  "e"  "e"  "e"
>
> gvec(4, letters[1:5], "b", "e", repeats = FALSE)
init Var1 Var2 final
[1,] "b"  "c"  "a"  "e"
[2,] "b"  "d"  "a"  "e"
[3,] "b"  "e"  "a"  "e"
[4,] "b"  "a"  "b"  "e"
[5,] "b"  "c"  "b"  "e"
[6,] "b"  "d"  "b"  "e"
[7,] "b"  "e"  "b"  "e"
[8,] "b"  "a"  "c"  "e"
[9,] "b"  "d"  "c"  "e"
[10,] "b"  "e"  "c"  "e"
[11,] "b"  "a"  "d"  "e"
[12,] "b"  "c"  "d"  "e"
[13,] "b"  "e"  "d"  "e"

:-)

-- Bert

On Mon, Sep 4, 2023 at 2:04 PM Bert Gunter <bgunter.4567 using gmail.com> wrote:

> Well, if strings with repeats (as you defined them) are to be excluded, I
> think it's simple just to use regular expressions to remove them.
>
> e.g.
> g <- function(ntimes, states, init, final, repeats = TRUE)
>    ## ntimes: integer, number of unique times
>    ## states: vector of unique states
>    ## init: initial state
>    ## final: final state
> {
> out <- do.call(paste0,c(init,expand.grid(rep(list(states), ntimes-2)),
> final))
> if(!repeats)
>    out[-grep(paste(paste0(states,states),  collapse = "|"),out)]
> else out
> }
> So:
>
> > g(4, LETTERS[1:5], "B", "E", repeats = FALSE)
>  [1] "BCAE" "BDAE" "BEAE" "BABE" "BCBE" "BDBE" "BEBE" "BACE"
>  [9] "BDCE" "BECE" "BADE" "BCDE" "BEDE"
>
> Perhaps not the most efficient way to do this, of course.
>
> Cheers,
> Bert
>
>
> On Mon, Sep 4, 2023 at 12:57 PM Eric Berger <ericjberger using gmail.com> wrote:
>
>> 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")
>>>>  [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)
>>>>>
>>>>> 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]
>>>>>
>>>>>
>>>>> 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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