Extract unique non-missing value from vector

Extract unique non-missing value from vector

uniquePresent(x, req.n1 = TRUE, na.pattern)

Arguments

x

A vector, either numeric or character.

req.n1

Require one unique value? If `TRUE` (default), an error is thrown if non-unique values found. If `FALSE`, all the unique values are returned.

na.pattern

In addition to NA-elements, what text strings should be considered missing? Default is empty strings and strings only containing white spaces (`na.pattern="^ *$"`).

Value

a vector of same class as `x`

Details

This function is particularly useful when combining data sets of which only some contain certain variables. uniquePresent with `req.n1=TRUE` makes sure the result is a single unique value (e.g., within subjects). A typical use is carrying subject-level covariates from one data set to another in a longitudinal analysis.