2
Hello, how can I select a row from a data frame that contains an expression but I don’t know which column that expression will be in?
1 answer
5
Use the function which. See the data set below:
library(ggplot2)
mpg
# A tibble: 234 x 11
manufacturer model displ year cyl trans drv cty hwy fl class
<chr> <chr> <dbl> <int> <int> <chr> <chr> <int> <int> <chr> <chr>
1 audi a4 1.8 1999 4 auto(l5) f 18 29 p compa…
2 audi a4 1.8 1999 4 manual(… f 21 29 p compa…
3 audi a4 2 2008 4 manual(… f 20 31 p compa…
4 audi a4 2 2008 4 auto(av) f 21 30 p compa…
5 audi a4 2.8 1999 6 auto(l5) f 16 26 p compa…
6 audi a4 2.8 1999 6 manual(… f 18 26 p compa…
7 audi a4 3.1 2008 6 auto(av) f 18 27 p compa…
8 audi a4 quatt… 1.8 1999 4 manual(… 4 18 26 p compa…
9 audi a4 quatt… 1.8 1999 4 auto(l5) 4 16 25 p compa…
10 audi a4 quatt… 2 2008 4 manual(… 4 20 28 p compa…
# ... with 224 more rows
If I roll
which(mpg == "a4", arr.ind = TRUE)
the result is
which(mpg == "a4", arr.ind = TRUE)
row col
[1,] 1 2
[2,] 2 2
[3,] 3 2
[4,] 4 2
[5,] 5 2
[6,] 6 2
[7,] 7 2
That is, the string a4 is in rows 1 to 7, column 2. So just rotate
mpg[which(mpg == "a4", arr.ind = TRUE)[, 1], ]
# A tibble: 7 x 11
manufacturer model displ year cyl trans drv cty hwy fl class
<chr> <chr> <dbl> <int> <int> <chr> <chr> <int> <int> <chr> <chr>
1 audi a4 1.8 1999 4 auto(l5) f 18 29 p compact
2 audi a4 1.8 1999 4 manual(m5) f 21 29 p compact
3 audi a4 2 2008 4 manual(m6) f 20 31 p compact
4 audi a4 2 2008 4 auto(av) f 21 30 p compact
5 audi a4 2.8 1999 6 auto(l5) f 16 26 p compact
6 audi a4 2.8 1999 6 manual(m5) f 18 26 p compact
7 audi a4 3.1 2008 6 auto(av) f 18 27 p compact
that the desired result is obtained.
Browser other questions tagged r
You are not signed in. Login or sign up in order to post.
You can make a loop by passing by column, and saving on which column and row is, with grepl.
– Manoel Galdino