Select rows from a data frame based on values in a vector

Question

I have data similar to this: ``` dt <- structure(list(fct = structure(c(1L, 2L, 3L, 4L, 3L, 4L, 1L, 2L, 3L, 1L, 2L, 3L, 2L, 3L, 4L), .Label = c("a", "b", "c", "d"), class = "factor"), X = c(2L, 4L, 3L, 2L, 5L, 4L, 7L, 2L, 9L, 1L, 4L, 2L, 5L, 4L, 2L)), .Names = c("fct", "X"), class = "data.frame", row.names = c(NA, -15L)) ``` I want to select rows from this data frame based on the values in the `fct` variable. For example, if I wish to select rows containing either "a" or "c" I can do this: ``` dt[dt$fct == 'a' | dt$fct == 'c', ] ``` which yields ``` 1 a 2 3 c 3 5 c 5 7 a 7 9 c 9 10 a 1 12 c 2 14 c 4 ``` as expected. But my actual data is more complex and I actually want to select rows based on the values in a vector such as ``` vc <- c('a', 'c') ``` So I tried ``` dt[dt$fct == vc, ] ``` but of course that doesn't work. I know I could code something to loop through the vector and pull out the rows needed and append them to a new dataframe, but I was hoping there was a more elegant way.…

Accepted Answer

Have a look at `?"%in%"`.

```
dt[dt$fct %in% vc,]
   fct X
1    a 2
3    c 3
5    c 5
7    a 7
9    c 9
10   a 1
12   c 2
14   c 4
```

You could also use `?is.element`:

```
dt[is.element(dt$fct, vc),]
```

Select rows from a data frame based on values in a vector

Solution

Problem