I have a large data set like this:

```
 df <- data.frame(group = c(rep(1, 3), rep(5, 3)), member = c(30, 10, 22, 21, 44, 15)) 

 group member
 1     30
 1     10
 1     22
 5     21
 5     44
 5     15

```

...

I want to order member within each group. The expected output should look like this:

```
 group member
 1     10
 1     22
 1     30
 5     15
 5     21
 5     44

```

...

Does anyone have idea about realizing this?