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

[Giles Innocent]

Or even:

which(lv)[1]

as lv is already a logical vector

Giles

On 2003.03.05 22:44 Spencer Graves wrote:
> 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
>> 
>> ______________________________________________
>> R-help at stat.math.ethz.ch mailing list
>> https://www.stat.math.ethz.ch/mailman/listinfo/r-help
> 
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