[R] how to find the location of the first TRUE of a logical vector

[Spencer Graves]

Also:

   which(lv == TRUE)[1]

Spencer Graves

Marc Schwartz wrote:
>>-----Original Message-----
>>From: r-help-bounces at stat.math.ethz.ch 
>>[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Jason Liao
>>Sent: Wednesday, March 05, 2003 3:36 PM
>>To: r-help at stat.math.ethz.ch
>>Subject: [R] how to find the location of the first TRUE of a 
>>logical vector
>>
>>
>>without having to check the vector element by element? Thanks a lot!
>>
>>Jason
>>
>>=====
>>Jason G. Liao, Ph.D.
>>Division of Biometrics
>>University of Medicine and Dentistry of New Jersey
>>335 George Street, Suite 2200
>>New Brunswick, NJ 08903-2688
>>phone (732) 235-8611, fax (732) 235-9777 
>>http://www.geocities.com/jg_liao
> 
> 
> 
> If 'lv' if your logical vector, you could use something like:
> 
> min(which(lv == TRUE))
> 
> which() would return a vector of the indices within 'lv' that match
> TRUE and of course min() will give you the lowest index value.
> 
> An example:
> 
> 
>>lv <- c(FALSE, FALSE, FALSE, TRUE, TRUE, FALSE, TRUE)
>>lv
> 
> [1] FALSE FALSE FALSE  TRUE  TRUE FALSE  TRUE
> 
>>min(which(lv == TRUE))
> 
> [1] 4
> 
> 
> HTH,
> 
> Marc Schwartz
> 
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