How to create lag columns using grouby

[Panda Lover]

Hi All,

I have a data frame looks like this:

C, Week, Quantity

a, 1, 3

a, 2, 4

a, 6, 7

b, 2, 4,

b, 3. 5

b. 5, 6

I would like to group the data frame by ['C1','C2'] and then use week and quantity information to compute lag information.

C, Week, Quantity, Lag

a, 1, 3 , NA

a, 2, 4,  3

a, 6, 7,  NA

b, 2, 4, NA

b, 3. 5, 4

b. 4, 6, 5.

b, 5, 8, NA

Can I use groupby's apply function to do this?

Or is there a efficient way to do this?

Thanks in advance,

[Tom Augspurger]

StackOverflow is typically better for these types of questions, since it's easier for others to find. Does something like this solve your problem?

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