# Imports
library(tidyverse)
library(ggplot2)

# Read in the CSV file
gdp <- read.csv('PATH_TO_CSV',header=T)

# Format the date column
gdp$Date <- strptime(gdp$Date, format = "%b %d %Y")

# Format Date
gdp$Date <- as.POSIXct(gdp$Date)

# Which dates to consider?
threshold <- "1970-01-01"

gdpReduced <-
  gdp %>%
  filter(Date > threshold) %>%
  mutate(isNegative = ifelse(Value < 0, TRUE, FALSE)) %>%
  mutate(prior1QuarterNegative = ifelse(lead(Value < 0), TRUE, FALSE)) %>%
  mutate(twoNegativeInARow = ifelse(isNegative & prior1QuarterNegative, TRUE, FALSE)) %>%
  transmute(Date = Date,
            Value = Value,
            twoNegativeInARow = twoNegativeInARow)

# Percentage occurence
occurences <-
  gdpReduced %>% filter(twoNegativeInARow)
occurenceRate <- nrow(occurences) / nrow(gdpReduced) # 7.2% as a prior probability