Is this a reasonably fast way to do an approximate match of a vector x to
values in a list?
match.approx <- function(x,list,tol=.0001)
sapply(apply(abs(outer(list,x,"-"))<tol,2,which),"[",1)
Thanks.
-Dan
On Mon, Mar 16, 2009 at 8:24 AM, Stavros Macrakis <macra...@alum.mit.edu>wrote:
> Well, first of all, seq(from=.2,to=.3) gives c(0.2), so I assume you
> really mean something like seq(from=.2,to=.3,by=.1), which gives
> c(0.2, 0.3).
>
> %in% tests for exact equality, which is almost never a good idea with
> floating-point numbers.
>
> You need to define what exactly you mean by "in" for floating-point
> numbers. What sort of tolerance are you willing to allow?
>
> Some possibilities would be for example:
>
> approxin <- function(x,list,tol) any(abs(list-x)<tol) # absolute
> tolerance
>
> rapproxin <- function(x,list,tol) (x==0 && 0 %in% list) ||
> any(abs((list-x)/x)<=tol,na.rm=TRUE)
> # relative tolerance; only exact 0 will match 0
>
> Hope this helps,
>
> -s
>
> On Mon, Mar 16, 2009 at 9:36 AM, Daniel Murphy <chiefmur...@gmail.com>
> wrote:
> > Hello:I am trying to match the value 0.3 in the sequence seq(.2,.3). I
> get
> >> 0.3 %in% seq(from=.2,to=.3)
> > [1] FALSE
> > Yet
> >> 0.3 %in% c(.2,.3)
> > [1] TRUE
> > For arbitrary sequences, this "invisible .3" has been problematic. What
> is
> > the best way to work around this?
>
[[alternative HTML version deleted]]
______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
