If I have a table like this:
user,v1,v2,v3
a,1,0,0
a,1,0,1
b,1,0,0
b,2,0,3
c,1,1,1
How to I turn it into this?
user,v1,v2,v3
a,2,0,1
b,3,0,3
c,1,1,1
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pnuts
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`aggregate(.~user, this, sum)`. – lukeA Sep 11 '15 at 19:34
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2possible duplicate of [How to sum a variable by group?](http://stackoverflow.com/questions/1660124/how-to-sum-a-variable-by-group) – aosmith Sep 11 '15 at 19:40
1 Answers
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We can use the base R aggregate for getting the sum of columns by group. Here, we use the formula method where . implies all other variables, while the 'user' on the RHS of ~ is the grouping variable. We specify the FUN=sum to get the sum of all other columns.
aggregate(.~user, df1, sum)
Or we can use data.table. We convert the 'data.frame' to 'data.table' (setDT(df1)), grouped by 'user', we loop (lapply) through the subset of data.table (.SD) and get the sum.
library(data.table)
setDT(df1)[, lapply(.SD, sum), by=user]
Or we use dplyr, grouped by 'user', we get the sum of all other columns within summarise_each.
library(dplyr)
df1 %>%
group_by(user) %>%
summarise_each(funs(sum))
akrun
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