How do I split the dataframe based on dates in R?

Question

x1<- split(df, cumsum(df$Date < 1900-01-01))

x2<- split(df, cumsum(df$Date >= 1945-01-01 & df$Date <= 1955-01-01))
x3<- split(df, cumsum(df$Date > 2000-01-01))

I am trying to split the data frame based on the above mentioned conditions. However, the functions only work for the first one, not on the other two.

Answer 1

Let's take this sample:

df <- data.frame(V1 = c("1800-01-01","1950-01-01","2005-01-01"))
df <- df %>% 
  mutate(V1 = as.Date(V1))

          V1
1 1800-01-01
2 1950-01-01
3 2005-01-01

Code:

library(tidyverse)
df <- df %>% 
  mutate(indic = case_when(
    V1 < "1900-01-01" ~ 1,
    V1 >= "1945-01-01" & V1 <= "1955-01-01" ~ 2,
    V1 > "2000-01-01" ~ 3,
    TRUE ~ 4
  )) 

list_of_df <- split(df, df$indic)

i = 1
MyF <- function(input){
  out <- as.data.frame(input)
  out <- out %>% select(-indic)
  nom <- paste0("dfE",i)
  assign(nom, out, envir = .GlobalEnv)
  i <<- i + 1
}

lapply(list_of_df, MyF)

This will create in your environment the dataframes dfE1 , dfE2 and dfE3 based on the conditions you used first (about the dates).

> dfE1
          V1
1 1800-01-01


> dfE2
          V1
2 1950-01-01


> dfE3
          V1
3 2005-01-01