Hi:
Here's one approach, although I imagine there are more efficient ways.
# A function to strip spaces and return the first three non-blank elements
of a string
keyset <- function(x) substr(gsub(' ', '', x)[1], 1, 3)
# Apply the function to the data frame to generate the key:
a$key <- sapply(a$product, keyset)
> a
date product sales key
1 20081201 a b c d e 1 abc
2 20081202 a b c g h t 2 abc
3 20081201 d e h a c e h g 3 deh
# Use aggregate to sum sales by key:
aggregate(sales ~ key, data = a, FUN = sum)
key sales
1 abc 3
2 deh 3
HTH,
Dennis
On Wed, Mar 9, 2011 at 6:02 PM, Hui Du <hui...@dataventures.com> wrote:
>
> 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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>
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