consolidating data frames in R

Question

Hi I have a lot of CSV files to process. Each file is generated by a run of an algorithm. My data always has one key and a value like this:

csv1:

Answer 1

Here is a solution. I am following all the excellent comments so far, and hopefully adding value by showing you how to handle any number of files. I am assuming you have all your csv files in the same directory (my.csv.dir below).

# locate the files
files <- list.files(my.csv.dir)

# read the files into a list of data.frames
data.list <- lapply(files, read.csv)

# concatenate into one big data.frame
data.cat <- do.call(rbind, data.list)

# aggregate
data.agg <- aggregate(value ~ index, data.cat, mean)

---

Edit: to handle your updated question in your comment below:

files     <- list.files(my.csv.dir)
algo.name <- sub("-.*", "", files)
data.list <- lapply(files, read.csv)
data.list <- Map(transform, data.list, algorithm = algo.name)
data.cat  <- do.call(rbind, data.list)
data.agg  <- aggregate(value ~ algorithm + index, data.cat, mean)