PreviousResult: Find Previous Test Result for Subject

In Transition: Characterise Transitions in Test Result Status in Longitudinal Studies

Find Previous Test Result for Subject

Description

get_prev_result() identifies the previous test result for individual subjects and timepoints in a longitudinal study.

add_prev_result() interpolates these previous test results into a data frame for further analysis.

Usage

add_prev_result(
  object,
  subject = "subject",
  timepoint = "timepoint",
  result = "result",
  prev_result = "prev_result"
)

get_prev_result(
  object,
  subject = "subject",
  timepoint = "timepoint",
  result = "result"
)

Arguments

object	a data.frame (or object coercible by as.data.frame() to a data frame) containing the data to be analysed.
subject	character, name of the column (of type integer or factor) identifying individual study subjects; default "subject".
timepoint	character, name of the column recording time points (as Dates) of testing of subjects; default "timepoint".
result	character, name of the column (of type ordered factor, or binary, see Details) recording test results; default "result".
prev_result	character, name to be used for a new column to record previous result; default "prev_result".

Details

See Transitions details.

Value

add_prev_result()	A data.frame based on object, with an added column named as specified by argument prev_result and of type ordered factor or integer depending on whether the results are semi-quantitiative or binary.
get_prev_result()	An ordered factor of length nrow(object), containing the values of the previous test results ordered in the exact sequence of the subject and timepoint in object.

See Also

data.frame, Dates, ordered factor.

Other transitions: PreviousDate, Transitions, uniques()

Examples

 ## Continuing example from `add_transitions()`
  # subject, timepoint and result arguments all defaults and required types
Blackmore |> str()

  # Previous test results as ordered factor
get_prev_result(Blackmore)

  # Previous test result as column of data frame
(Blackmore <- add_prev_result(Blackmore)) |> head(32)

rm(Blackmore)

Transition documentation built on Feb. 11, 2026, 5:07 p.m.