I would like to obtain a cumulative sum through years and for each entity.

Here below an example, and what I have tried so far:

data<-data.frame(id=c("a","a","a","b","a","b","b"),cars=c(1,1,1,1,1,1,1),year=c(2001,2001,2002,2003,2003,2003,2004))

I have tried :

library(tidyverse)
library(stringr)
library(dplyr)
library(tidyr)

data %>% group_by(id,year) %>% mutate(csum = (cumsum(cars))) %>% top_n(1, csum)
  id     cars  year  csum
  <chr> <dbl> <dbl> <dbl>
1 a         1  2001     2
2 a         1  2002     1
3 a         1  2003     1
4 b         1  2003     2
5 b         1  2004     1

This is what I would like:

  id     cars  year  csum
  <chr> <dbl> <dbl> <dbl>
1 a         1  2001     2
2 a         1  2002     3
3 a         1  2003     4
4 b         1  2003     2
5 b         1  2004     3

Thank you very much.

>Solution :

The function you need is aggregate, you can use it this way :

aggregate(x=data$cars, #column on which you want to apply a function
          by=list(id=data$id,year=data$year),#grouping variables
          FUN=sum)#function to apply