How to use an index to read multiple files at a time? - r

Question

I want R to read the five files with names like
"alpha_rarefaction_8000_0.txt" ... "alpha_rarefaction_12000_0.txt"
and write it as
"alpha8000" ... "alpha12000", respectively.
I used the following code, but it did not work. Please help. What's wrong with my codes?
I tried to search like "how to use index in R function" or "how to write executable loop in R", but nothing helps. What kind of search strategy should I use to get effective results where searching the answers on Google?
for(i in seq(8000,12000,by=1000)) {
paste("rare",i,sep="")<-read.table(paste("alpha_rarefaction",i,"0.txt",sep="_"))
}
or
read.rare<-function(i){
paste("rare",$i,sep="")<-read.table(paste("alpha_rarefaction",$i,"0.txt",sep="_"))
}
i<-seq(8000,12000,by=1000)
read.rare(i)

Answer 1

I would recommend you read the files into a list, possibly doing it this way -
## create the sequence for the file names
s <- 8:12 * 1e3
# [1] 8000 9000 10000 11000 12000
## create the full file names from the sequence above
files <- sprintf("alpha_rarefaction_%d_0.txt", s)
# [1] "alpha_rarefaction_8000_0.txt" "alpha_rarefaction_9000_0.txt"
# [3] "alpha_rarefaction_10000_0.txt" "alpha_rarefaction_11000_0.txt"
# [5] "alpha_rarefaction_12000_0.txt"
## Now we can loop the file names, reading the data into a list
## and setting the names for each element
datalist <- setNames(lapply(files, read.table), paste0("alpha", s))
This will keep all the data frames in a list, which will make working with them later a lot easier. You can access them individually with the $ operator. They have names
names(datalist)
[1] "alpha8000" "alpha9000" "alpha10000" "alpha11000" "alpha12000"
so datalist$alpha9000, for example, accesses the second data set (and alternatively with datalist[[2]]).