Cumulative total by group

Question

For the following dataset:

d = data.frame(date = as.Date(as.Date(\'2015-01-01\'):as.Date(\'2015-04-10\'), origin = \"1970-01-01\"),
               group = re         


        

Answer 1

As this question was tagged with data.table, you are probably looking for (a modification of @Franks comment).

setDT(d)[order(date), new := cumsum(value), by = group]

This will simultaneously rearrange the data by date (not sure if needed, if not, you can get rid of order(date)) and update your data set in place utilizing the := operator

Answer 2

Is this it?

sp <- split(d, d$group)
res <- lapply(seq_along(sp), function(i) cumsum(sp[[i]]$value))
res <- lapply(seq_along(res), function(i){
        sp[[i]]$c.sum <- res[[i]]
        sp[[i]]
    }) 
res <- do.call(rbind, res)
res

Answer 3

This should work

library(dplyr)
d %>% 
  group_by(group) %>% 
  arrange(date) %>% 
  mutate(Total = cumsum(value))

Answer 4

If you just want cumulative sums per group, then you can do

transform(d, new=ave(value,group,FUN=cumsum))

with base R.