Demonstrates the idiosyncratic behavior of NA values in R

r_na_examples

# The below demonstrates the madness of R's treatment of NA values.
# Some examples taken from https://stackoverflow.com/questions/25100974/na-matches-na-but-is-not-equal-to-na-why/25101796

# Logical examples

NA %in% NA
# [1] TRUE

NA == NA
# [1] NA

NA | TRUE
# [1] TRUE

NA_real_ | TRUE
# [1] TRUE

NA_integer_ | TRUE
# [1] TRUE

NA | FALSE
# [1] NA

NA_real_ | FALSE
# [1] NA

NA_integer_ | FALSE
# [1] NA

TRUE | paste(NA)
# Error in TRUE | paste(NA) : 
# operations are possible only for numeric, logical or complex types

# Matching examples

match(NA, NA)
# [1] 1

match(NA, NA_real_)
# [1] 1

match(NA_character_, NA_real_)
# [1] 1

match(paste(NA), NA)
# [1] NA

gsub("NA", "", NA)
# [1] NA

gsub("NA", "", paste(NA))
# [1] ""

is.na(NA)
# [1] TRUE

is.na(paste(NA))
# [1] FALSE

# Other examples

identical(NA, NA)
# [1] TRUE

eval(NA)
# [1] NA

is.na(eval(NA))
# [1] TRUE