[R] How do I do a conditional sum which only looks between certain date criteria

[arun]

If the data is like:
dat1 <- read.table(text="date, user, items_bought
2013-01-01, x, 2
2013-01-02, x, 1
2013-01-05, x, 1
2013-01-06, x, 5
2013-01-11, x, 3
2013-01-14, x, 1
2013-01-01, y, 1
2013-01-02, y, 1
2013-01-03, y, 0
2013-01-04, y, 5
2013-01-05, y, 6
2013-01-06, y, 1",sep=",",header=TRUE,stringsAsFactors=FALSE)
dat1$date <- as.Date(dat1$date)

res3 <- unsplit(lapply(split(dat1, dat1$user), function(x) {
    date1 <- seq(min(x$date), max(x$date), by = "1 day")
    indx <- (seq_along(date1) - 1)%/%3
    indx1 <- date1 %in% x$date
    x$cum_times_bought_3_days <- ave(x$items_bought, indx[indx1], FUN = cumsum)
    indx2 <- seq(0, length(indx), 4)
    indx3 <- c(FALSE, diff(indx[indx1]) > 0)
    x[indx3, 4] <- x[indx3, 4] + indx[indx2]
    x
}), dat1$user)
##Here also, the same confusion persists.


A.K.


On Thursday, June 5, 2014 11:09 PM, arun <smartpink111 at yahoo.com> wrote:
Hi,
The expected output is confusing.
dat1 <- read.table(text="date, user, items_bought
2013-01-01, x, 2
2013-01-02, x, 1
2013-01-03, x, 0
2013-01-04, x, 0
2013-01-05, x, 3
2013-01-06, x, 1
2013-01-01, y, 1
2013-01-02, y, 1
2013-01-03, y, 0
2013-01-04, y, 5
2013-01-05, y, 6
2013-01-06, y, 1",sep=",",header=TRUE,stringsAsFactors=FALSE)

##Assuming that the data is ordered by date and no gaps in date
res1 <- unsplit(lapply(split(dat1, dat1$user), function(x) {
    indx <- (seq(nrow(x)) - 1)%/%3
    x$cum_items_bought_3_days <- ave(x$items_bought, indx, FUN = cumsum)
    x
}), dat1$user)



##expected output
res2 <- unsplit(lapply(split(dat1, dat1$user), function(x) {
    indx <- (seq(nrow(x)) - 1)%/%3
    x$cum_items_bought_3_days <- ave(x$items_bought, indx, FUN = cumsum)
    indx2 <- seq(0, length(indx), by = 4)
    x[indx2, 4] <- x[indx2, 4] + indx[indx2]
    x
}), dat1$user)

A.K.


Say I have data that looks like
date, user, items_bought
2013-01-01, x, 2
2013-01-02, x, 1
2013-01-03, x, 0
2013-01-04, x, 0
2013-01-05, x, 3
2013-01-06, x, 1
2013-01-01, y, 1
2013-01-02, y, 1
2013-01-03, y, 0
2013-01-04, y, 5
2013-01-05, y, 6
2013-01-06, y, 1

to get the cumulative sum per user per data point I was doing
data.frame(cum_items_bought=unlist(tapply(as.numeric(data$items_bought), data$user, FUN = cumsum)))

output from this looks like
date, user, items_bought
2013-01-01, x, 2
2013-01-02, x, 3
2013-01-03, x, 3
2013-01-04, x, 3
2013-01-05, x, 6
2013-01-06, x, 7
2013-01-01, y, 1
2013-01-02, y, 2
2013-01-03, y, 2
2013-01-04, y, 7
2013-01-05, y, 13
2013-01-06, y, 14

However I want to restrict my sum to only add up those that happened within 3 days of each row (relative to the user). i.e. the output needs to look like this:
date, user, cum_items_bought_3_days
2013-01-01, x, 2
2013-01-02, x, 3
2013-01-03, x, 3
2013-01-04, x, 1
2013-01-05, x, 3
2013-01-06, x, 4
2013-01-01, y, 1
2013-01-02, y, 2
2013-01-03, y, 2
2013-01-04, y, 6
2013-01-05, y, 11
2013-01-06, y, 12