Type conversion between character and numeric is a constant need in clinical data — strings come in from CDISC specs, numbers come back out for analysis.
Two directions to know: character to numeric for analysis, numeric to character for report layout.
In both directions, invalid values (e.g. "ABC" in a numeric column) need to become missing rather than crashing the program.
SAS uses input(char, informat.) for character-to-numeric and put(num, format.) for numeric-to-character.
R uses as.numeric() and as.character() directly in both tidyverse and base dialects.
This lesson demonstrates both conversions on a mixed dataset that includes one invalid string ("ABC") so we can see how each language handles the edge case.