Dear all,

Trying to extract a few rows for each element of a list of data.frames, I'm puzzled by the following behaviour,


d <- lapply(1:4,  function(i) data.frame(x=rnorm(5), y=rnorm(5)))
str(d)

lapply(d, "[", i= c(1)) # fine,  this extracts the first columns
lapply(d, "[", j= c(1, 3)) # doesn't do nothing ?!

library(plyr)

llply(d, "[", j= c(1, 3)) # same


Am i misinterpreting the meaning of "j", which I thought was an argument of the method "[.data.frame"?


args(`[.data.frame`)
function (x, i, j, drop = if (missing(i)) TRUE else length(cols) ==
   1)


Many thanks,

baptiste

_____________________________

Baptiste AuguiƩ

School of Physics
University of Exeter
Stocker Road,
Exeter, Devon,
EX4 4QL, UK

Phone: +44 1392 264187

http://newton.ex.ac.uk/research/emag

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