How to create a new variable excluding missing date values?

Question

I am trying to write a R code for creating a new variable which excludes the missing date values from two variables, of class POSIXct/POSIXt. So, for example, if 'date1' and 'date2' are my two variables comprising mostly, of dates and some missing values. And I want to store all the non - missing date values in a new variable, 'var'. I believe my code will look something like this:

if date1 = 'NA' then
var = date2 
else var = date1
end

I am well aware that if-else statements can't be used in this context. However, I am not sure how else to go about writing this code. Any help is appreciated! :)

score 0 · Answer 1 · answered Aug 01 '19 at 19:26

Suppose you have this data (chosen to contain a few potential edge cases). BTW, it's good form to include a sample of your data or data like it in a replicable form. See here: How to make a great R reproducible example

my_data <- data.frame(
  date1 = as.Date(c("2020-01-01", "2020-01-01", "2020-01-01", NA, NA), "%Y-%m-%d"),
  date2 = as.Date(c("2020-01-02", "2020-01-02", NA, "2020-01-02", NA), "%Y-%m-%d")
)

> my_data
       date1      date2
1 2020-01-01 2020-01-02
2 2020-01-01 2020-01-02
3 2020-01-01       <NA>
4       <NA> 2020-01-02
5       <NA>       <NA>

Here are a few approaches to do what you asked.

1) In Base R, you can use ifelse, but it has a troublesome way of converting dates to numbers and takes some work to bring them back. See How to prevent ifelse() from turning Date objects into numeric objects

my_data$base = as.Date(ifelse(is.na(my_data$date1), 
                              as.character(my_data$date2),
                              as.character(my_data$date1)), "%Y-%m-%d")

2) dplyr's if_else doesn't do this, so you can use:

my_data$if_else = dplyr::if_else(is.na(my_data$date1), 
                              my_data$date2,
                              my_data$date1)

3) dplyr::coalesce is a nice way of doing this more concisely:

my_data$coalesce = dplyr::coalesce(my_data$date1, my_data$date2)

Output

> my_data
       date1      date2     ifelse    if_else   coalesce
1 2020-01-01 2020-01-02 2020-01-01 2020-01-01 2020-01-01
2 2020-01-01 2020-01-02 2020-01-01 2020-01-01 2020-01-01
3 2020-01-01       <NA> 2020-01-01 2020-01-01 2020-01-01
4       <NA> 2020-01-02 2020-01-02 2020-01-02 2020-01-02
5       <NA>       <NA>       <NA>       <NA>       <NA>

All of these methods work! Thank you so much for your help! I will be sure to follow the guidelines for uploading a reproducible code. Once again, thank you so much for your help! — Bing96, Aug 02 '19 at 03:36

How to create a new variable excluding missing date values?

1 Answers1