[R] Identifying one or more TRUE in the middle of an array

[William Revelle]

Yet another way which returns the row and column of the items you want

rc <- which(t(x[,-c(1,ncol(x))]),arr.ind=TRUE)  #this identifies the rows and columns but is one column off
rc[,1] <- rc[,1] +1 #this adjusts the columns
colnames(rc) <- c("col","row")
rc   #show them

Bill




On Jun 6, 2014, at 5:27 PM, ONKELINX, Thierry <Thierry.ONKELINX at inbo.be> wrote:

> Here is my solution.
> 
> falses <- which(!x)
> first.false <- head(falses, 1)
> last.false <- tail(falses, 1)
> which(x[first.false:last.false]) + first.false - 1
> 
> 
> Best regards,
> 
> ir. Thierry Onkelinx
> Instituut voor natuur- en bosonderzoek / Research Institute for Nature and Forest
> team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance
> Kliniekstraat 25
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> Thierry.Onkelinx at inbo.be
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> 
> ________________________________________
> Van: r-help-bounces at r-project.org [r-help-bounces at r-project.org] namens Fisher Dennis [fisher at plessthan.com]
> Verzonden: vrijdag 6 juni 2014 23:45
> Aan: r-help at stat.math.ethz.ch
> Onderwerp: [R] Identifying one or more TRUE in the middle of an array
> 
> R 3.1.0
> OS X
> 
> Colleagues
> 
> I have an array (I am using T/F rather than TRUE/FALSE for convenience) that could have patterns like:
>        c(T, T, T, F, F, F, T, F, T, T, T)              ## T at either end, a single T in the middle
>        c(F, F, F, F, F, T, F, F, T, T, T)              ## T at the tail end, a single T in the middle
>        c(T, T, T, F, F, T, T, F, F, F, F)              ## T at the front end, two T in the middle
>        c(T, T, T, F, F, T, T, F, T, F, F)              ## T at the front end, three T in the middle (not contiguous)
>        c(F, F, F, F, F, T, F, F, F, F, F)              ## no T at either end, a single T in the middle
> There might (or might not) be one or more T at the beginning (or the end).
> There might or might not be one or more T in the middle (not in a series that continues to either end) and the position of these T values varies.
> 
> I am trying to identify the indices (if any) of these T values in the middle
> A brute force approach would be to strip off any contiguous T values from each end, then look for any remaining T values.  Can anyone propose a more clever approach?
> 
> Dennis
> 
> Dennis Fisher MD
> P < (The "P Less Than" Company)
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> 
> 
> 
> 
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William Revelle		           http://personality-project.org/revelle.html
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