How to detect start and end of constant periods?

Question

I'm trying to plot recession shading periods in R. Consider the following example, where recession periods are recognized as 1, and non-recession periods are 0.

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  

Can anyone help me to pick up the starting dates and ending dates of the recession periods? Expected output:

Start                 End
1918-09-01     1919-03-01
1920-02-01     1920-05-01

Similar question has been asked a few years ago, but I think the answer is not able to solve this question.

Answer 1

data <- read.csv('recession.csv')

# Add new first and last row to the data, to enable the detection of change
# in the beginning and in the end of the time series.
data <- rbind(c(NA, ifelse(data$Recession[1] == 1, yes = 0, no = NA)),
              data,
              c(NA, ifelse(data$Recession[length(data$Recession)] == 1, 0, NA)))

# Create new data frame containing the start and end of each recession period.
# The periods are detected via built in diff function which calculates 
# differences between all consecutive values in a vector.
recession.periods <- data.frame(
    Start = data$Date[which(diff(data$Recession, lag = 1) == 1) + 1],
    End = data$Date[which(diff(data$Recession, lag = 1) == -1)])