[R] non-consing count

[Ista Zahn]

Hi Sam,

Here is one alternative, which is at least faster:

system.time(count.0 <- length(which(x == 0)))
system.time(count.1 <- sum(x == 0))
all.equal(count.0, count.1)

Best,
Ista

On Fri, Jan 4, 2013 at 10:30 AM, Sam Steingold <sds at gnu.org> wrote:
> Hi,
> to count vector elements with some property, the standard idiom seems to
> be length(which):
> --8<---------------cut here---------------start------------->8---
> x <- c(1,1,0,0,0)
> count.0 <- length(which(x == 0))
> --8<---------------cut here---------------end--------------->8---
> however, this approach allocates and discards 2 vectors: a logical
> vector of length=length(x) and an integer vector in which.
> is there a cheaper alternative?
> Thanks!
>
> --
> Sam Steingold (http://sds.podval.org/) on Ubuntu 12.04 (precise) X 11.0.11103000
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