I have two dataframes. One is called `y25.29`

, where `head(y25.29)`

gives:

```
pidp quantile
1 68575973 61
2 69180553 10
3 70003965 43
4 70069925 13
5 70432365 18
6 70510565 35
```

with # of rows = 310.

The other is called `data.07`

, where `head(data.07)`

gives:

```
pidp fiyrl
1 68002045 2000.000
2 68035365 26000.000
3 68058485 0.000
4 68058489 0.000
5 68064605 24795.568
6 68064609 8868.146
```

and # of rows = 5,883.

What I'm looking to do is group all rows in `y25.29`

by quantile, and, using `pidp`

as an identifier, create a dataframe that returns the average of `fiyrl`

from `data.07`

of those individuals that have the same quantile in `y25.29`

. So, for example, all individuals that have `quantile = 34`

will have a value of `fiyrl`

. The new dataframe will hopefully have a column with all the `quantiles`

and a column with the average of `fiyrl`

that corresponds to all individuals in that quantile.

I have no idea on where to start. Thanks!!