Re: [R] How x[, 'colname1'] is implemented?

Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com > -Original Message- > From: r-help-boun...@r-project.org > [mailto:r-help-boun...@r-project.org] On Behalf Of Peng Yu > Sent: Thursday, December 31, 2009 2:16 PM > To: r-h...@stat.math.ethz.ch > Subject: [R]

Re: [R] How x[, 'colname1'] is implemented?

On Fri, Jan 1, 2010 at 4:24 PM, milton ruser wrote: > Hi Peng, > > If I undertood your point, try this: > > x<-runif(10) > y<-runif(10) > z<-runif(10) > w<-runif(10) > > myDF<-data.frame(cbind(x,y,z,w)) > myDF > > myDF[,c("w","z")] Thank you! But this is not what I'm asking. I want to know how R

Re: [R] How x[, 'colname1'] is implemented?

Hi Peng, If I undertood your point, try this: x<-runif(10) y<-runif(10) z<-runif(10) w<-runif(10) myDF<-data.frame(cbind(x,y,z,w)) myDF myDF[,c("w","z")] Happy new year miltinho On Thu, Dec 31, 2009 at 5:15 PM, Peng Yu wrote: > I don't see where describes the implementation of '[]'. > >

[R] How x[, 'colname1'] is implemented?

I don't see where describes the implementation of '[]'. For example, if x is a matrix or a data.frame, how the lookup of 'colname1' is x[, 'colname1'] executed. Does R perform a lookup in the a hash of the colnames? Is the reference O(1) or O(n), where n is the second dim of x? __