Recode Missing or Ambiguous UDS in a Subject Use PatternSource:
Replace all missing UDS
"o" in a use pattern string
recode_missing_visits( use_pattern, missing_is = "o", missing_becomes = c("+", "", "-") )
A character string showing the daily, by visit, or weekly substance use pattern for a single subject
Which single character is used to mark missing UDS in a use pattern string? Defaults to
How should missing UDS be treated? Defaults to marking the subject as positive for that missing period. Options are
""for ignore, or
"-"for negative (note that this last option should only be used in case where the "missing" UDS is a regular and expected artefact of the study design and the preceding and following UDS are both negative).
A character string with all missing UDS values (marked as
unless a different value is supplied to
missing_is) replaces by the
value supplied to
At current, we allow for many symbols in the use pattern "word", such as "_" for missing by study design, "o" missing for protocol non-compliance (the most common form of missing), "+" for positive, "-" for negative, and "*" for mixed positive and negative results (this usually comes up when the visit represents multiple days and there are both positive and negative results in those days; for example, a subject is tested weekly; they provided a positive test on Tuesday but came back to provide a negative test the following day).
pattern_char <- "__++++*o-------+--+-o-o-o+o+" # Default: change all missing weeks to positive recode_missing_visits(pattern_char) #>  "__++++*+-------+--+-+-+-++++" # Other example: remove all weeks with no UDS by design recode_missing_visits(pattern_char, missing_is = "_", missing_becomes = "") #>  "++++*o-------+--+-o-o-o+o+"