[R] How to sum and group data by DATE in data frame

[clair.crossupton at googlemail.com]

Dear all,

Lets say I have a data frame as follows:


> Date <- as.Date(c('2006-08-23', '2006-08-30', '2006-09-06', '2006-09-13', '2006-09-20'))
> Income <- c(73.79, 72.46, 76.32, 72.43, 72.62)
> data.frame(Date, Income)
        Date Income
1 2006-08-23  73.79
2 2006-08-30  72.46
3 2006-09-06  76.32
4 2006-09-13  72.43
5 2006-09-20  72.62
>

is there a way to group the data by month (summing the values in each
month), i.e.

Date       Income
2006-08  146.25
2006-09  221.37

Thanks in advance,
C.C.