Create new column in dataframe

[Scott]

Hi everyone,

I have a dataframe I am trying to manipulate to create two new columns and drop 1 based on the sum function the does a conditional group by and I cannot find any example online. Below is the dataframe I have:

Date id class amount
1/12/2002 1 L 5
1/12/2002 1 H 6
1/12/2002 1 L 7
1/12/2002 2 L 3
1/01/2003 1 L 2
1/01/2003 1 H 8
1/01/2003 2 H 7
1/01/2003 2 L 9
1/01/2003 2 L 1

I'm looking to create a new column, L_class that sums the amount grouped by date and ID when class = 'L' and then do the same thing for H_class when class = 'H' and then drop the class field. the data frame should look like this.

Date id L_class H_class
1/12/2002 1 12 6
1/12/2002 2 3
1/01/2003 1 2 8
1/01/2003 2 10 7

I've tried googling how to do it and I have a function that does the calculation but not one that can create a new variable based on the condition. Does anyone have any ideas or know of an example online?

Thanks for any help