How to initialize N named, empty data frames into a list in R?

Question

I want to initialize N named, empty data frames that have X rows and Y columns in each and put them in a list. I will fill them later by adding computed vectors. It’s a newbie question I know, but how does one do that? For example:

my.names <- c("G", "H", "J")
N <- 3
my.list <- ???  ## how?

(edited in light of replies ...) My reason for this approach is I have a big loop that creates N vectors each time through the loop. I need to save these results each iteration. I planned to do something like:

for(i in 1:N) my.list[[i]] <- my.vec[i]

on each pass in the loop. A 3D data frame or matrix would also do the same thing.

Answer 1

Maybe you want to initialize a three-dimensional array instead?

myarr <- array(,dim=c(3,5,10))
for (j in 1:5) for (k in 1:10) myarr[,j,k] <- rnorm(3)

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List of empty data.frames. I don't think there's a good reason to initialize a list of data.frames, but here's how it would be done:

An "empty" data.frame is created by data.frame():

setNames(replicate(3,data.frame()),my.names)
# $G
# data frame with 0 columns and 0 rows

# $H
# data frame with 0 columns and 0 rows

# $J
# data frame with 0 columns and 0 rows

A data.frame with rows and columns must have some values, for example NA:

nr  <- 4
nc  <- 4
ndf <- length(my.names)
setNames(replicate(ndf,as.data.frame(matrix(,nr,nc)),simplify=FALSE),my.names)