Loading data from RData files into a single data table

Question

I'm trying to load data from data frame objects of all .RData files in a specified directory into a single data table. This is how I've tried to do this:

library(data.table)

fileList <- list.files("../cache/FLOSSmole", pattern="\\.RData$", full.names=TRUE)
dataset <- rbindlist(lapply(fileList, FUN=function(file) {as.data.table(load(file))}))

However, the result is different from the expected (single data table containing all data) - it contains just names of data frame objects from the source .RData files:

> str(dataset)
Classes ‘data.table’ and 'data.frame':  39 obs. of  1 variable:
 $ V1: chr  "lpdOfficialBugTags" "lpdLicenses" "lpdMilestones" "lpdSeries" ...
 - attr(*, ".internal.selfref")=<externalptr>
> head(dataset)
                        V1
1:      lpdOfficialBugTags
2:             lpdLicenses
3:           lpdMilestones
4:               lpdSeries
5:             lpdProjects
6: lpdProgrammingLanguages

What am I doing wrong? Your help is greatly appreciated!

My R environment:

> sessionInfo()
R version 3.1.0 (2014-04-10)
Platform: x86_64-pc-linux-gnu (64-bit)

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8
 [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
 [9] LC_ADDRESS=C               LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

other attached packages:
[1] data.table_1.9.2

loaded via a namespace (and not attached):
[1] plyr_1.8.1    Rcpp_0.11.1   reshape2_1.4  stringr_0.6.2 tools_3.1.0

Answer 1

.RData is a saved workspace, it may contain data frames, but it is not a data frame. How many data frames are there in each .RData? You can load multiple .RData files and they add to the current workspace. Just load them all then merge or rbind the data.frames once they are in your current workspace

# lapply(FileList,function(x) load(x)) # Changed to a for loop, I guess the lapply was only loading into the lapply environment which disappears when the function ends
for (i in 1:length(FileList)) {
   load(FileList[i])
}
my.list <- vector(length(ls()),mode="list")
for (i in 1:length(ls())) {
    my.list[[i]] <- get(ls()[i])
}
my.rbind <- do.call(rbind,my.list)

This is one way. An easier way would be to save individual tables as delimited text files in the first place.