Ok, I have a matrix of values with certain identifiers, such as:

```
A  2
B  3
C  4
D  5
E  6
F  7
G  8

```

I would like to pull out a subset of these values (using R) based on a list of the identifiers ("B", "D", "E") for example, so I would get the following output:

```
B  3
D  5
E  6

```

I'm sure there's an easy way to do this (some sort of apply?) but I can't seem to figure it out. Any ideas? Thanks!