Mutate column showing increasing/decreasing value compared to previous period

Question

Let's say I have a df like this

Dealer Period    Revenue
A      August    10
B      August    10
A      September 30
B      September 5

How can I use mutate function to create a column which shows the compared result of Revenue to previous period.

The result i want is something like

Dealer Period    Revenue Compared_result
A      August    10      N/A
B      August    10      N/A
A      September 30      20
B      September 5       -5

In base R, `ave(df$Revenue, df$Dealer, FUN=function(x) c(NA,diff(x)))` — Ronak Shah, Aug 07 '18 at 06:53

score 2 · Accepted Answer · answered Aug 07 '18 at 06:51

 library(dplyr)
 df %>% group_by(Dealer) %>% 
        mutate(Comp=Revenue-lag(Revenue))

  # A tibble: 4 x 4
  # Groups:   Dealer [2]
    Dealer Period    Revenue  Comp
    <fct>  <fct>       <int> <int>
   1 A      August         10    NA
   2 B      August         10    NA
   3 A      September      30    20
   4 B      September       5    -5

Mutate column showing increasing/decreasing value compared to previous period

1 Answers1