On 3/17/2009 11:26 AM, Daniel Murphy wrote:
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)
If you are willing to assume that the list values are all multiples of 2*tol, then it's easy: just divide both x and list by 2*tol, round to nearest integer, and use the regular match function.
If not, it becomes harder; I'd probably use a solution like yours. Duncan Murdoch
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
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