Aggregate Weekly Data in R

Question

I am sure this is straight forward but I just cant seem to get it to work. I have a data frame that represents daily totals. I simply want to sum the totals by week, retai

Answer 1

A solution with the lubridate library:

library(lubridate)
Lines <- "date,amt
2009-04-01,45
2009-04-02,150
2009-04-03,165
2009-04-13,165
2009-04-14,45
2009-04-15,45
2009-05-15,45"
df <- read.csv(textConnection(Lines))

If you don't need 0 for missing weeks it's simple:

weeks <- week(df$date)
sums <- tapply(df$amt, weeks, sum)
# 14  15  16  20 
#360 210  45  45 

To put zeros for missing weeks:

span <- min(weeks):max(weeks)
out <- array(0, dim = length(span), dimnames = list(span))
out[dimnames(sums)[[1]]] <- sums
# 14  15  16  17  18  19  20 
#360 210  45   0   0   0  45