[R] Method Guidance

[Bill Dunlap]

Suppose your data were represented as parallel vectors "time" and "type",
meaning that at time[i] a type[i] event occurred.  You didn't say what you
wanted if there were a run of "A" or "B".  If you are looking for the time
span between the last of a run of one sort of event and the first of a run
of the other sort of event then the following can be used.

f <- function(time, type, fromType, toType) {
    # return times of (fromTime) last of a run of 'fromType' and
    # (toTime) first of subsequent run of 'toType for each such transition.
    stopifnot(length(time)==length(type),
              !anyNA(type),
              !anyNA(time),
              !is.unsorted(time),
              length(fromType)==1,
              length(toType)==1)
    i <- seq_len(length(time)-1)
    iBeforeChange <- which((type[i] == fromType) & (type[i+1] == toType))
    data.frame(fromTime=time[iBeforeChange], toTime=time[iBeforeChange+1L])
}

E.g.,

> d <- data.frame(time=c(101,102,102,105,107,111,115),
type=c("A","A","B","A","B","B","A"))
> d
  time type
1  101    A
2  102    A
3  102    B
4  105    A
5  107    B
6  111    B
7  115    A
> f(time=d$time, type=d$type, fromType="A", toType="B")
  fromTime toTime
1      102    102
2      105    107
> with(.Last.value, toTime - fromTime)
[1] 0 2
> f(time=d$time, type=d$type, fromType="B", toType="A")
  fromTime toTime
1      102    105
2      111    115
> with(.Last.value, toTime - fromTime)
[1] 3 4

With the dplyr package you can avoid the index 'i' by using lag() inside of
mutate().  E.g.,

> d |> mutate(AtoB = (lag(type)=="A" & type=="B"))
  time type  AtoB
1  101    A FALSE
2  102    A FALSE
3  102    B  TRUE
4  105    A FALSE
5  107    B  TRUE
6  111    B FALSE
7  115    A FALSE

-Bill


On Tue, Jan 11, 2022 at 4:56 PM Jeff Reichman <reichmanj using sbcglobal.net>
wrote:

> R-Help Forum
>
>
>
> Looking for a little guidance. Have an issue were I'm trying to determine
> the time between when Event A happened(In days) to when a subsequent Event
> B
> happens. For Example at Time 1 Evat A happens and subsequently Event B
> happens at the same day (0) and the next day (1) then Event A happens again
> at time 4 and Event B happens the next day and 3 days later so on and so
> forth. I gather there is no function that will do that so I suspect I will
> need to grate so sour of do while loop?  Any suggestions?
>
>
>
>
>
> Time      Event_A               Event_B               Time_B
>
> 1              1                              1
> 0
>
> 2              0                              1
> 1
>
> 3              0                              0
> 0
>
> 4              1                              0
> 0
>
> 5              0                              1
> 1
>
> 6              0                              0
> 0
>
> 7              0                              1
> 3
>
> 8              1                              1
> 0
>
> 9              0                              0
> 0
>
> 10           0                              1
> 2
>
>
>
>
> Jeff Reichman
>
>
>         [[alternative HTML version deleted]]
>
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