[R] own function: computing time

[William Dunlap]

No, the desired points are not a subset of the convex hull.
E.g., x=c(0,1:5), y=c(0,1/(1:5)).

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com


> -----Original Message-----
> From: William Dunlap
> Sent: Wednesday, October 10, 2012 9:46 AM
> To: 'tonja.krueger at web.de'; r-help at r-project.org
> Subject: RE: [R] own function: computing time
> 
> Are the points you are looking for (those data points with no other data
> points above or to the right of them) a subset of the convex hull of the
> data points?  If so, chull(x,y) can quickly give you the points on the convex
> hull (typically a fairly small number) and you can look through them for
> the ones you want.
> 
> Bill Dunlap
> Spotfire, TIBCO Software
> wdunlap tibco.com
> 
> 
> > -----Original Message-----
> > From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf
> > Of tonja.krueger at web.de
> > Sent: Wednesday, October 10, 2012 3:16 AM
> > To: r-help at r-project.org
> > Subject: [R] own function: computing time
> >
> > Hi all,
> >
> > I wrote a function that actually does what I want it to do, but it tends to be very slow
> for
> > large amount of data. On my computer it takes 5.37 seconds for 16000 data points and
> > 21.95 seconds for 32000 data points. As my real data consists of 18000000 data points
> it
> > would take ages to use the function as it is now.
> > Could someone help me to speed up the calculation?
> >
> > Thank you, Tonja
> >
> > system.time({
> > x <- runif(32000)
> > y <- runif(32000)
> >
> > xy <- cbind(x,y)
> >
> > outer <- function(z){
> > !any(x > z[1] & y > z[2])}
> > j <- apply(xy,1, outer)
> >
> > plot(x,y)
> > points(x[j],y[j],col="green")
> >
> > })
> >
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