I have a dataframe df:

```
ID    Var1     Var2
1     1.2        4
1     2.1        6
1     3.0        7
2     1.3        8
2     2.1        9
2     3.2        13

```

I want to find the pearson correlation coefficient value between `Var1` and `Var2` for every `ID`

So the result should look like this:

```
ID    Corr_Coef
1     0.98198
2     0.97073

```

update:

Must make sure all columns of variables are `int` or `float`