Transition (version 1.0.1)

PreviousResult: Find Previous Test Result for Subject

Description

get_prev_results() 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"
)

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.

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.

See Also

data.frame, Dates, ordered factor.

Other transitions: PreviousDate, Transitions, uniques()

Examples

# \dontshow{
Blackmore <- transform(Blackmore, timepoint = as.Date("2000-01-01") + round(age * 365.25),
    result = cut(exercise, breaks = seq(0, 30, 2), labels = paste0("<=", seq(0, 30, 2)[-1]),
        include.lowest = TRUE, ordered_result = TRUE))
# }

 ## 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)