max() function on date format in R-CodePudding

I have a column in my dataset which is formatted as dates. I am aiming to obtain the most recent date by using the max() function. The date column is formatted like (ex. 21.12.2018), and I have used the folowing lines of code:

MD$Date<- as.Date(MD$Date, "%d.%m.%Y")
analysis_date <- max(MD$Date)

Howevere, analysis_date returns the value NA. Any tips?

CodePudding user response：

Here an exemple using dplyr from tidyverse:

# package
library(dplyr)

# Sample database
MD <- data.frame(
  Date = c("21.12.2018", NA, "20.12.2018", "19.12.2018")
  )

# Get the most recent date
MD |> 
  slice_max(
    as.Date(Date, "%d.%m.%Y")
  )

CodePudding user response：

I think the reason it returns the NA is that your date is in character you need to convert your dataset from character to date format.

my_dates_update <- as.Date(my_dates)   # Convert character to Date
  
  class(my_dates_update) # Check the class of updated dates, it should return date as type
  
  min(my_dates_updated) # Earliest date
  
  max(my_dates_updated) # Latest date