Using grep in R to delete rows from a data.frame
dataframe, r, row
Solution
You can use TRUE/FALSE subsetting instead of numeric.
`grepl` is like grep, but it returns a `logical` vector. Negation works with it.
d[!grepl("K",d$z),]
x y z
1 1 1 apple
2 1 2 pear
3 1 3 banana
4 1 4 A
5 1 5 B
6 1 6 C
7 1 7 D
8 1 8 E
9 1 9 F
10 1 10 G
Problem
I have a dataframe such as this one: ``` d <- data.frame(x=1, y=1:10, z=c("apple","pear","banana","A","B","C","D","E","F","G"), stringsAsFactors = FALSE) ``` I'd like to delete some rows from this dataframe, depending on the content of column z: ``` new_d <- d[-grep("D",d$z),] ``` This works fine; row 7 is now deleted: ``` new_d x y z 1 1 1 apple 2 1 2 pear 3 1 3 banana 4 1 4 A 5 1 5 B 6 1 6 C 8 1 8 E 9 1 9 F 10 1 10 G ``` However, when I use grep to search for content that is not present in column z, it seems to delete all content of the dataframe: ``` new_d <- d[-grep("K",d$z),] new_d # [1] x y z # <0 rows> (or 0-length row.names) ``` I would like to search and delete rows in this or another way, even if the character string I am searching for is not present. How to go about this?