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rcsvcommentsfread
Bhavneet sharma
Bhavneet sharma

Reputation: 427

Using "fread", how to eliminate comment line from csv?

I have to read a CSV file which has some comment lines(start with #) along with data rows. fread function is used to read this CSV file.

config <- fread("Configuration.csv")

CSV file snapshot

In this file number of lines are not fixed they might be changed. How to read the CSV without these comment lines.

Thanks in Advance!!!

Upvotes: 4

Views: 5457

Answers (2)

Grzegorz Sionkowski
Grzegorz Sionkowski

Reputation: 529

You can try to clean the data using grep before, not after:

config <- fread("grep -v '^#' Configuration.csv")

UPDATED:

If the aim of using fread() is to convert the data to data.table only, you can use read.table() instead with default comment.char="#" and then convert the result into data.table:

config <- as.data.table(read.table(header = TRUE, "Configuration.csv"))

Upvotes: 5

Wimpel
Wimpel

Reputation: 27732

updated answer

I assume you are using windows... if so, you can feed the results from findstr to fread().
The data from the orinal answer is saved to test.csv.

data.table::fread( cmd = 'findstr "^[^#]" test.csv', sep = "\n", header = FALSE )

#                V1
#1:  line,with,data
#2: line2,with,data

findstr /b /v test.csv gives the same result

When on linux, you can (probably) pass the output from a grep command to fread().

old answer

This sulution is not very helpful when dealing with only one file, but is will help when reading in multiple files using lapply()

text = "line,with,data
#commentline,with,data
line2,with,data"

data.table::fread( text, sep = "\n", header = FALSE )[!grepl( "^#", V1 )]

Upvotes: 2

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