CODEWITHSUNDEEP
pythonrlist-comprehension
hhh
hhh

Reputation: 52850

Python list-comprehension in R?

I want this in R:

fsC=[read.table(x) for x in Sys.glob('./Trial7/*.csv')]

i.e. trying to read the content of each file to a separate vector where vectors belong to a data structure.

Python

[file(x, 'r').read() for x in glob.glob('./Trial7/*.csv')]

or better actually

[file(x, 'r') for x in glob.glob('./Trial7/*.csv')]

but I think you got the point...

Upvotes: 1

Views: 2406

Answers (2)

Richie Cotton
Richie Cotton

Reputation: 121127

You have two questions here. First, "given a vector of filenames, how do you read those files into R?".

Here's your list of filenames

trial7_files <- Sys.glob("Trial7/*.csv") 
#if you prefer to specify the names using regular expressions, try 
trial7_files <- dir("Trial7", "\\.csv$")

As previously noted, lapply is the best way of reading in the files.

fsC <- lapply(trial7_files, read.csv)

This gives you a list of data frames, and leads to your next question. "How do you combine a list of data frames with the same columns into one data frame?"

The standard way to do this is with do.call and rbind. First, it's useful to make a note of how many rows there are in each dataset.

n_records <- sapply(fsC, nrow)
fsC <- do.call(rbind, fsC)

That's your problem solved, though you probably want a column telling you which file each row came from.

fsC$source <- rep(trial7_files, n_records)

Upvotes: 7

zch
zch

Reputation: 15278

Use sapply to "map" vectors:

sapply(Sys.glob('./Trial7/*.csv'), read.table) -> fsc

Upvotes: 5

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