grep things and counting line number in R

Question

[saadleeshehreen]

Hi, I am a beginner in R. I want to grep "x" from file1 and pipe it with line count command to know how many lines in file1 contain "X". What is the command for it?

[h.mon]

Why do you need to do this in R, if there are many (bash + grep, perl, python; to name just three) better tools for the task?

[cpad0112]

I understand that OP wants grep and wc functions in R for "x". IMO, this is kind of looking for duplicates i.e count the lines where X is present more than once. This function might do that: (Assumption is that X is present once in a line and X is not part of a string).

length(df[df=="x"])

Answer 1

[zx8754]

Let's say we have below file:

file1.txt

texst1  test1
test2   test1
test3   test1
test4   xtexst1
test5x  test1

We can read the file, and use grepl to search for "x". grepl returns TRUE for matches, then we can sum to get the count.

myFile <- readLines("file1.txt")
sum(grepl(pattern = "x", x = myFile))
# [1] 3

Answer 2

[Kevin Blighe]

Shell / BASH:

cat test
echo on
hello world
hello world
alo mundo
alo mundo
hola mundo
hola mundo
echo off

Then, load R:

R

system("grep -e 'hello' test | wc -l")
2

system("grep -e 'echo' test | wc -l")
2

system("grep -e 'echo' test")
echo on
echo off

system("grep -e 'mundo' test | wc -l")
4

system("grep -e 'mundo' test")
alo mundo
alo mundo
hola mundo
hola mundo

system() allows you to invoke operating system commands.

You can also read the file into R but it would help if it were TSV or CSV, an there run the grep() R command.

Kevin

[saadleeshehreen]

Hi,

I was looking for a command in R. I know 'grep' and 'wc -l' work in shell.

[Kevin Blighe]

Please re-read my answer. The system() function in R allows you to do what you want.

[saadleeshehreen]

Oh..thanks a lot .got it