recode_missing_visits {CTNote}

Recode Missing or Ambiguous UDS in a Subject Use Pattern

Description

Replace all missing UDS "o" in a use pattern string

Usage

recode_missing_visits(
  use_pattern,
  missing_is = "o",
  missing_becomes = c("+", "", "-")
)

Arguments

use_pattern

A character string showing the daily, by visit, or weekly substance use pattern for a single subject

missing_is

Which single character is used to mark missing UDS in a use pattern string? Defaults to "o".

missing_becomes

How should missing UDS be treated? Defaults to marking the subject as positive for that missing period. Options are "+" for positive, "" 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).

Details

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).

Value

A character string with all missing UDS values (marked as "o" unless a different value is supplied to missing_is) replaces by the value supplied to missing_becomes.

Examples

  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 = "")