[R] Vector searching and counting speed optimization

[Eric Archer]

Richard,

Thanks!  I never would've thought of using sum() to count the TRUEs in a 
logical vector, but it makes perfect sense.

Cheers,
e.

Richard M. Heiberger wrote:
> sum() looks faster to me
>
> tmp <- as.logical(rbinom(100,1,.5))
>
>   
>> system.time(for (i in 1:10000) length(tmp[tmp]))
>>     
> [1] 0.09 0.00 0.09   NA   NA
>   
>> system.time(for (i in 1:10000) sum(tmp))
>>     
> [1] 0.03 0.00 0.03   NA   NA
>
> I am running on Windows XP
>
>   
>> Sys.getenv()[20]
>>     
>                             PROCESSOR_IDENTIFIER 
> "x86 Family 15 Model 2 Stepping 4, GenuineIntel" 
>   
>
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