# Input and output
# Reading and writing data frames
Data frames are R's tabular data structure. They can be written to or read from in a variety of ways.
This example illustrates a couple common situations. See the links at the end for other resources.
Before making the example data below, make sure you're in a folder you want to write to. Run
getwd() to verify the folder you're in and read
?setwd if you need to change folders.
set.seed(1) for (i in 1:3) write.table( data.frame(id = 1:2, v = sample(letters, 2)), file = sprintf("file201%s.csv", i) )
Now, we have three similarly-formatted CSV files on disk.
We have three similarly-formatted files (from the last section) to read in. Since these files are related, we should store them together after reading in, in a
file_names = c("file2011.csv", "file2012.csv", "file2013.csv") file_contents = lapply(setNames(file_names, file_names), read.table) # $file2011.csv # id v # 1 1 g # 2 2 j # # $file2012.csv # id v # 1 1 o # 2 2 w # # $file2013.csv # id v # 1 1 f # 2 2 w
To work with this list of files, first examine the structure with
str(file_contents), then read about stacking the list with
?rbind or iterating over the list with
# Further resources
?write.table to extend this example. Also:
- Plain-text table formats
To construct file paths, for reading or writing, use
dir to see what files are in a directory.