I have several data frames that look similar to the following data frame (with much more columns):

```
id col1 col2 col3 col4 col5
1   4    3    5    4    A
1   3    5    4    9    Z
1   5    8    3    4    H
2   6    9    2    1    B
2   4    9    5    4    K
3   2    1    7    5    J
3   5    8    4    3    B
3   6    4    3    9    C

```

I want to calculate the standard deviation across specific columns (let's say col2 to col4) grouped by the id. I do not know the column index in every data frame. I only know the names for the columns I want to calculate the standard deviation for.

Is there a way I could do that easily? My original data frames contain around 20 columns and I only want the standard deviation for 10 columns with specific column names grouped by the id.

On top, it would be nice if I can directly add the calculated standard deviations to my data frame as a new column according to the id, looking like this:

```
id col1 col2 col3 col4 col5 SD
1   4    3    5    4    A   SD1
1   3    5    4    9    Z   SD1
1   5    8    3    4    H   SD1
2   6    9    2    1    B   SD2
2   4    9    5    4    K   SD2
3   2    1    7    5    J   SD3
3   5    8    4    3    B   SD3
3   6    4    3    9    C   SD3

```