I'm working through an R tutorial and suspect that I have to use one of these functions but I'm not sure which (Yes I researched them but until I become more fluent in R terminology they are quite confusing).
In my working directory there is a folder "specdata". Specdata contains hundreds of CSV files named 001.csv - 300.csv.
The function I am working on must count the total number of rows for an inputed number of csv files. So if the argument in the function is 1:10
and each of those files has ten rows, return 100.
Here's what I have so far:
complete <- function(directory,id = 1:332) {
setpath <- paste("/Users/gcameron/Desktop",directory,sep="/")
setwd(setpath)
csvfile <- sprintf("%03d.csv", id)
file <- read.csv(csvfile)
nrow(file)
}
This works when the ID argument is one number, say 17. But, if I input say 10:50 as an argument, I receive an error:
Error in file(file, "rt") : invalid 'description' argument
What should I do to be able to count the total number of rows from the inputed ID parameter?
read.csv
expects to read just one file, so you need to loop over files, a R idiomatic way of doing so is to use sapply
:
nrows <- sapply( csvfile, function(f) nrow(read.csv(f)) )
sum(nrows)
For example, here is a rewrite of your complete
function:
complete <- function(directory,id = 1:332) {
csvfiles <- sprintf("/Users/gcameron/Desktop/%s/%03d.csv", directory, id)
nrows <- sapply( csvfiles, function(f) nrow(read.csv(f)) )
sum(nrows)
}