[R] Script help: Determining Time Difference between two data points.
William Dunlap
wdunlap at tibco.com
Tue Jul 17 18:49:29 CEST 2012
Does this do what you want?
> firstInRun <- function(x) c(TRUE, x[-1] != x[-length(x)])
> lastInRun <- function(x) c(x[-1] != x[-length(x)], TRUE)
> f <- function(data, condition) {
+ with(data, data.frame(startDate = Date[firstInRun(condition)],
+ endDate = Date[lastInRun(condition)]))
+ }
> f(d, d$Score > 150)
startDate endDate
1 2008-04-30 23:58:00 2008-05-01 07:35:00
2 2008-05-01 14:20:00 2008-05-01 14:20:00
3 2008-05-01 16:01:00 2008-05-09 16:43:00
4 2008-05-09 18:22:00 2008-05-09 22:44:00
5 2008-05-10 01:03:00 2008-05-12 16:01:00
6 2008-05-12 18:09:00 2008-05-12 18:09:00
7 2008-05-12 20:44:00 2008-05-13 09:14:00
8 2008-05-13 12:03:00 2008-05-13 12:03:00
> .Last.value$endDate - .Last.value$startDate
Time differences in secs
[1] 27420 0 693720 15720 226680 0 45000 0
attr(,"tzone")
[1] ""
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
> Behalf Of APOCooter
> Sent: Tuesday, July 17, 2012 5:54 AM
> To: r-help at r-project.org
> Subject: [R] Script help: Determining Time Difference between two data points.
>
> I have the following data (a subset of the real data set):
>
> structure(list(Date = structure(c(1209625080, 1209641460, 1209652500,
> 1209676800, 1209682860, 1209692100, 1209706980, 1209722580, 1209726300,
> 1209739620, 1209762780, 1209765720, 1209770520, 1209791040, 1209812580,
> 1209829920, 1209837180, 1209848160, 1209854640, 1209859440, 1209870780,
> 1209887760, 1209901080, 1209921660, 1209929280, 1209945600, 1209957240,
> 1209980280, 1210001760, 1210017000, 1210021140, 1210034820, 1210042800,
> 1210048980, 1210061520, 1210074480, 1210081200, 1210089300, 1210095960,
> 1210104120, 1210110900, 1210110900, 1210118400, 1210126980, 1210134180,
> 1210142640, 1210156080, 1210164180, 1210176840, 1210183740, 1210196820,
> 1210202400, 1210217700, 1210229280, 1210238280, 1210259520, 1210274100,
> 1210283100, 1210291560, 1210291620, 1210309260, 1210333440, 1210349520,
> 1210360440, 1210376580, 1210382520, 1210389960, 1210398240, 1210406580,
> 1210413240, 1210439220, 1210444800, 1210453140, 1210461900, 1210467060,
> 1210475160, 1210488900, 1210500000, 1210504980, 1210512780, 1210523820,
> 1210530900, 1210544340, 1210555800, 1210563120, 1210564980, 1210572600,
> 1210585620, 1210595520, 1210602840, 1210613820, 1210618200, 1210633260,
> 1210640940, 1210650240, 1210663560, 1210677660, 1210686960, 1210695240,
> 1210705380), class = c("POSIXct", "POSIXt"), tzone = ""), Score = c(80L,
> 11L, 81L, 152L, 130L, 122L, 142L, 20L, 1L, 31L, 93L, 136L, 128L,
> 112L, 48L, 57L, 92L, 108L, 100L, 107L, 81L, 37L, 47L, 70L, 114L,
> 125L, 99L, 46L, 108L, 106L, 111L, 75L, 75L, 136L, 36L, 13L, 35L,
> 71L, 105L, 113L, 116L, 116L, 94L, 130L, 102L, 19L, 1L, 33L, 78L,
> 89L, 115L, 130L, 117L, 105L, 0L, 36L, 80L, 130L, 124L, 124L,
> 66L, 75L, 57L, 94L, 124L, 165L, 170L, 158L, 127L, 116L, 107L,
> 118L, 150L, 96L, 101L, 59L, 38L, 46L, 77L, 83L, 54L, 61L, 60L,
> 55L, 110L, 127L, 129L, 87L, 61L, 70L, 85L, 110L, 131L, 151L,
> 123L, 50L, 77L, 100L, 135L, 151L)), .Names = c("Date", "Score"
> ), row.names = c(NA, 100L), class = "data.frame")
>
> I am trying to write code that will check to see if the score is above a
> certain point, and then if it is, calculate how long it stays above that
> point.
>
> I'm not incredibly familiar with R, or programming in general. Here is my
> attempt:
>
> # TimeDiff is supposed to be a vector containing time objects. The first is
> subtracted from the last to give a time difference.
> #TimeTable is supposed to be a vector of time differences.
> for(i in seq(along=Data$Score)){
> if(Data$Score[i]>=140){
> (Data$Date[i])->TimeDiff[length(TimeDiff)+1]}
> # I put the calculation of the time difference in this loop because when the
> score drops below 140, that”run” of high scores is ended.
> if(Data$Score[i]<140){
> if(TimeDiff != 0){
> TimeTable[length(TimeTable)+1]<-TimDiff[length(TimeDiff)]-
> TimeDiff[2]
> TimeDiff<-0
> }
> }
> }
>
> I'm certain there is a more elegant and efficient way to do this, but this
> should at least be functional. It isn't, however. If I copy and paste this
> into R, I don't get any unexpected symbol errors. However, I do get a
> message saying that there were 50 or more warnings. They're all:
>
> “In if (TimeDiff != 0) { ... :
> the condition has length > 1 and only the first element will be used”
>
> I don't know what that means, nor how to fix it.
>
> Additionally, TimeDiff ends up being a bunch of numbers of numeric class.
> However, when I manually subtract one time from another, I get a time
> difference (which is what I'm looking for).
>
> Also, TimeTable ends up being 0 at the end, instead of a vector of time
> differences
>
> Any help on getting this working would be greatly appreciated.
>
> --
> View this message in context: http://r.789695.n4.nabble.com/Script-help-
> Determining-Time-Difference-between-two-data-points-tp4636743.html
> Sent from the R help mailing list archive at Nabble.com.
>
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