Message-ID: <Law11-F73crenlB5VC400019e12@hotmail.com>
Date: 2003-05-01T00:51:50Z
From: R A F
Subject: List of lists? Data frames? (Or other data structures?)
Hi, I'm faced with the following problem and would appreciate some
advice.
I could have a data frame x that looks like this:
aa bb
a 1 "A"
b 2 "B"
The advantage of this is that I could access all the individual
components easily. Also I could access all the rows and columns
easily.
Alternatively, I could have a list of lists that looks like this:
xprime <- list()
xprime$a <- list()
xprime$b <- list()
xprime$a$aa <- 1
xprime$a$bb <- "A"
xprime$b$aa <- 2
xprime$b$bb <- "B"
etc.
If speed is important, would a list of lists be faster than a data
frame? (I know, for example, that scan is supposed to be faster than
read.table, but I don't know if that is related to issues with data
frames.)
My problem with a list of lists, though, is that if I want to access
all the bb subcomponents, a naive method like this one failed:
y <- c( "a", "b" )
xprime[[ y ]]$bb (Does not work)
So to get all the bb subcomponents I seem to need to loop, which may
slow things down (presumably). But maybe people here know of a way.
Finally what would be the "best" way given the constraint of quick
access to all rows, columns and individual components?
I'd appreciate your thoughts and comments. Thanks very much.