Types and Missing Values
Missing Values
Skipping NA
NA marks missing data. Logical masks and is.na let a script select only known values.
Program
Play the script to watch the missing score get excluded before the average is computed.
missing_values.R
scores <- c(10, NA, 8)
known <- !is.na(scores)
average <- mean(scores[known])
cat(average, "\n", sep = "")
NA
`NA` represents a missing value in R.
is.na
`is.na(scores)` returns `TRUE` where values are missing.
logical mask
A logical vector can select matching positions from another vector.