R help - Apr 2010 - Vectorized forms of isTRUE, identical and all.equal?

Dear all,

I'm wondering if there exist vectorized forms of 'isTRUE()',
'identical()' and 'all.equal()'.  My problem is that I wish to
test if
each element of a vector is equal to a particular value (or
numerically close), whilst dealing carefully with NAs and so on.
However, using sapply() with identical() is very slow because it makes
so many separate function calls:

x = rbinom(1e4, 1, 0.5)

system.time(sapply(x, function(x) isTRUE(all.equal(x, 0))))

system.time(abs(x)  < .Machine$double.eps^0.5)

The latter version is fast, but potentially dangerous.  Any suggestions?

Thanks,

Robin

--
Robin Evans
Statistics Department
University of Washington
www.stat.washington.edu/~rje42

Hi,

On Wed, Apr 7, 2010 at 5:44 PM, Robin Evans <rje42 at stat.washington.edu>
wrote:
> Dear all,
>
> I'm wondering if there exist vectorized forms of 'isTRUE()',
> 'identical()' and 'all.equal()'. ?My problem is that I wish
to test if
> each element of a vector is equal to a particular value (or
> numerically close), whilst dealing carefully with NAs and so on.
> However, using sapply() with identical() is very slow because it makes
> so many separate function calls:
>
> x = rbinom(1e4, 1, 0.5)
>
> system.time(sapply(x, function(x) isTRUE(all.equal(x, 0))))
>
> system.time(abs(x) ?< .Machine$double.eps^0.5)
>
> The latter version is fast, but potentially dangerous. ?Any suggestions?
Why is it dangerous? Because some values in x can be NA?

-steve
>
> Thanks,
>
> Robin
>
> --
> Robin Evans
> Statistics Department
> University of Washington
> www.stat.washington.edu/~rje42
>
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>


-- 
Steve Lianoglou
Graduate Student: Computational Systems Biology
 | Memorial Sloan-Kettering Cancer Center
 | Weill Medical College of Cornell University
Contact Info: http://cbio.mskcc.org/~lianos/contact