i have two message ids say 197, 198 . I want to subset the data frame for those users who have got the messages from these ids. I only want those rows which contains both these message ids.

The data frame is `m`

I have used the code

```
a = c(197,198)
n = subset(m$userid,m$mid %in% a)

```

I also tried 

```
n = m[m$mid == 197 & m$mid == 198]

```

both of these codes are creating OR output whereas I want AND output.

here is the sample dataframe:

```
mid userid opened

197 1022    Y
197 1036    N
197 1100    Y
198 1000    Y
198 1022    N
198 1036    Y

```

I want output as records containing userid for both mid 197 &198

```
mid userid opened
197 1022    Y
197 1036    N
198 1022    N
198 1036    Y

```