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.
tomsihap 