Part 2 : complete()
Write a function that reads a directory full of files and reports the number of completely observed cases in each data file. The function should return a data frame where the first column is the name of the file and the second column is the number of complete cases.
Datas returned are shown here.
complete <- function(directory, id = 1:332) {
files <- list.files(directory, full.names = 1)
complete_files <- data.frame(id=NA, nobs=NA)
for (i in id) {
complete_files[i, 1] <- i
complete_files[i, 2] <- sum(complete.cases(read.csv(files[i])))
}
complete_files
}
Relatively simple, in this function we start by reading the files from the given directory and creating an empty data.frame headed with column names (id and nobs).
Console output:
> complete("specdata", 1)
id nobs
1 1 117
> complete("specdata", c(2, 4, 8, 10, 12))
id nobs
1 NA NA
2 2 1041
3 NA NA
4 4 474
5 NA NA
6 NA NA
7 NA NA
8 8 192
9 NA NA
10 10 148
11 NA NA
12 12 96
> complete("specdata", 30:25)
id nobs
(...)
22 NA NA
23 NA NA
24 NA NA
25 25 463
26 26 586
27 27 338
28 28 475
29 29 711
30 30 932
> complete("specdata", 3)
id nobs
1 NA NA
2 NA NA
3 3 243
The code works well, but there is an issue: the loop takes every id numbers from 1 to ID.
After debuging the function with debug(complete) to see the trace, I guess since it is a data.frame, rows are completed from 1 and writing on the spaces #01, #02… #id.
A kind of solution :
complete <- function(directory, id = 1:332) {
files <- list.files(directory, full.names = 1)
complete_files <- data.frame(id=integer(), nobs=integer())
for (i in id) {
complete_files[i, 1] <- i
complete_files[i, 2] <- sum(complete.cases(read.csv(files[i])))
}
complete_files[complete.cases(complete_files),]
}
> complete("specdata", 25:30)
id nobs
25 25 463
26 26 586
27 27 338
28 28 475
29 29 711
30 30 932
Better, but not correct: we have just removed the NA rows from the data.frame, but we need to rewrite the data.frame to make the results starting at the data.frame id=1.
What we need to do is to get the length of the id vector, not the id itself.
My solution :
complete <- function(directory, id = 1:332) {
files <- list.files(directory, full.names = 1)
complete_files <- data.frame(id=integer(), nobs=integer())
for (i in 1:length(id)) {
complete_files[i,1] <- id[i]
complete_files[i, 2] <- sum(complete.cases(read.csv(files[id[i]])))
}
complete_files
}
Although this works and the correction is simple, there was a slight difficulty : my first try was nesting loops (for i in id > for j in length(id)) to keep either the current ID from the vector and the current ID from the data.frame. Obviously, at every vector ID it rewrote length(id) times into the data.frame, erasing the datas.
