
Hi All,

                I have a data frame like

a = data.frame(date = c(20081201, 20081202, 20081201), product = c("a b c d e", "a b c g h t", "d e h a c e h g"), sales = c(1, 2, 3))

                Now I want to aggregate the sales by part of the a$product. 'Product' is the product name, a string separated by a space. The key in my aggregate function is first three items in "product" field. In my example, the key is "a b c", "a b c" and "d e h", respectively. Do you know how to do it? I thought an awkward way which needed several function calls (like strsplit, lapply, paste etc)  to manipulate the string in 'product' field. I guess there could be some more elegant way to do it.

                Thanks in advance.


HXD

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