[R] as.integer(TRUE)

Prof Brian Ripley ripley at stats.ox.ac.uk
Tue Sep 14 08:15:51 CEST 2004

On Mon, 13 Sep 2004, Tamas K Papp wrote:

> The fact that as.integer(TRUE) is 1 (and that for FALSE, it gives
> zero) is a really nice feature, eg when constructing piecewise
> functions (for example, as in -x*(x<0)+x*(x>=0)) and for many other
> things.
> Since I haven't found a reference about this, I just wanted to ask
> whether this is officialy part of the language or just a side effect
> (ie I want to know whether it is here to stay and if it is prudent to
> use this).

Well, you are actually using as.numeric(TRUE) there.  That is documented 
to be 1 (and as.numeric(FALSE) to be 0), in the Blue Book p.100.

Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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