R pick up the starting date and ending date of the Recession period [closed]

Answer 1

Using the rleid() function from the data.table package:

library(data.table)
data.table(DF)[, .(min(Date), max(Date)), by = .(rleid(Recession), Recession)][
  Recession == 1, .(Start = V1, End = V2)]

        Start        End
1: 1918-09-01 1919-03-01
2: 1920-02-01 1920-05-01

Explanation

The first data.table expression finds start and end dates of all periods. rleid() is a convenience function for generating a run-length type id column to be used in grouping operations.

data.table(DF)[, .(min(Date), max(Date)), by = .(rleid(Recession), Recession)]

   rleid Recession         V1         V2
1:     1         1 1918-09-01 1919-03-01
2:     2         0 1919-04-01 1920-01-01
3:     3         1 1920-02-01 1920-05-01

The second expression picks only the Recession periods and returns the Start and End dates.

Data

DF <- readr::read_table(
  "Date           Recession  
  1918-09-01     1  
  1918-10-01     1  
  1918-11-01     1  
  1918-12-01     1  
  1919-01-01     1  
  1919-02-01     1  
  1919-03-01     1  
  1919-04-01     0  
  1919-05-01     0  
  1919-06-01     0  
  1919-07-01     0  
  1919-08-01     0  
  1919-09-01     0  
  1919-10-01     0  
  1919-11-01     0  
  1919-12-01     0  
  1920-01-01     0  
  1920-02-01     1  
  1920-03-01     1  
  1920-04-01     1  
  1920-05-01     1  "
)