Embed two-dimensional arrays as part of higher-dimensional arrays in R

My questions concerns how to cleanly deal with a bunch of data I have.

I'm running an experiment with 4 conditions. There will be 20 participants in each condition, and when each completes the experiment, I'm left with a text file that has 600 rows, and 7 columns. The 600 rows correspond to 600 trials that each person completes. The 7 columns refer to variables that are measured on each trial.

So my data for each person look something like this (except there are 600 rows):

394        b               a                0          9773              1        1436
114        a               b                0          3595              1        1246
432        b               a                0          1272              1        1061
209        a               a                1          3514              1        120

In order to run my analyses, it would be really helpful if I could get all these text files into the one object called "data" that would have the following dimensions:

• Experimental condition (1-4)
• Participant number (1-20)
• Trial number (1-600)
• Variable (1-7)

My files have names like "ii-wm-long_1316994934_7_1.txt", where the "ii-wm-long" part identifies their experimental condition, and the last number (1 here) identifies their participant number.

At the moment my code looks like this:

#Get the names of the text files in the results folder
files <- list.files()

#Conditions - which ones correspond to which numbers
condition.def <- c("开发者_如何学Cii-wm-long","ii-wm-short","wm-ii-long","wm-ii-short")
#1 = ii-wm-long
#2 = ii-wm-short
#3 = wm-ii-long
#4 = wm-ii-short

#This is where everything will be stored
data <- array(NA,dim=c(4,20,600,7),dimnames=c("condition","participantNumber","trialNumber","experimentalvariable"))

#Loop for each participant's file
for (n in 1:length(files)){

#What condition is the person in?
condition <- unlist(strsplit(files[n],"\\_"))[1]
condition <- grep(condition,condition.def)

#What is their participant number (of the people in that condition)?
ppt <- as.integer(unlist(strsplit(unlist(strsplit(files[n],"\\_")),"\\."))[4])

#Read the text file into the array
data[condition,ppt,,] <- read.table(files[n],sep="\t",header=F,nrows=600,col.names=c("stimulus","category","category.choice","category.correct","category.time","memory.present","memory.time"))

}

I receive an error:

Error in data[condition, ppt, , ] <- read.table(files[n], sep = "\t",  : 
  incorrect number of subscripts

I've read up on cbind and abind, and can't seem to figure out how they would allow me to read the data in one-by-one.

What is the correct way to take a 2D array, and turn it into the last 2 dimensions of a 4D array?

read.table returns a data.frame, so at the very least you would need to wrap it in as.matrix:

data[condition,ppt,,] <- 
    as.matrix(read.table(files[n], sep="\t", header=FALSE, nrows=600, 
                         col.names=c("stimulus", "category", "category.choice",
                                     "category.correct", "category.time", 
                                     "memory.present", "memory.time")))

But, this is pretty fragile since you are going directly from I/O into an array slice, and you should put in some sanity checks so you know the input is as expected, the file exists, and so on.