How to get the actual values from cumulative numbers from day wise data in R

Question

Below is my data-frame:

I wanted to get the actual entry as follows:

Answer 1

In R, you can use diff() as a arugment in the transform() :

transform(df, entry = c(cum_entry[1], diff(cum_entry)))

#  Day cum_entry entry

#1   1         0     0

#2   2         1     1

#3   3         2     1

#4   3         2     0

#5   4         3     1

#6   4         3     0

In dplyr, we can use lag() as an argument in the mutate function :

library(dplyr)

df %>%  mutate(entry = cum_entry - lag(cum_entry, default = 0))

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