[R] Find the first values in vector

[David Winsemius]

On Nov 9, 2009, at 1:44 PM, Grzes wrote:

>
> Hi !
> I have a vector:
> vec= TRUE  TRUE  TRUE  TRUE FALSE FALSE FALSE FALSE TRUE  TRUE  FALSE
> and I'm looking for a method which let me get only the first values  
> equal
> TRUE from this vector. It means that I want to get a vector:
> vec_out =  TRUE  TRUE  TRUE  TRUE
>
> or posictions values = TRUE: vec_out = 1,2,3,4

?rle

 > vec[ 1:rle(vec)$lengths[1] ]
[1] "TRUE" "TRUE" "TRUE" "TRUE"


Although that approach would faid if the first element were "FALSE".

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David Winsemius, MD
Heritage Laboratories
West Hartford, CT