Find Previous Test Result for Subject

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"
)

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".

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.

Details

See Transitions details.

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()
#> 'data.frame':	945 obs. of  6 variables:
#>  $ subject  : Factor w/ 231 levels "100","101","102",..: 1 1 1 1 1 2 2 2 2 2 ...
#>  $ age      : num  8 10 12 14 15.9 ...
#>  $ exercise : num  2.71 1.94 2.36 1.54 8.63 0.14 0.14 0 0 5.08 ...
#>  $ group    : Factor w/ 2 levels "control","patient": 2 2 2 2 2 2 2 2 2 2 ...
#>  $ timepoint: Date, format: "2008-01-01" "2009-12-31" ...
#>  $ result   : Ord.factor w/ 15 levels "<=2"<"<=4"<"<=6"<..: 2 1 2 1 5 1 1 1 1 3 ...

  # Previous test results as ordered factor
get_prev_result(Blackmore)
#>   [1] <NA> <=4  <=2  <=4  <=2  <NA> <=2  <=2  <=2  <=2  <NA> <=2  <=2  <=6  <NA>
#>  [16] <=2  <=4  <=4  <NA> <=4  <=8  <=2  <NA> <=2  <=2  <=2  <=2  <NA> <=2  <=2 
#>  [31] <=2  <=2  <NA> <=2  <=2  <=2  <=6  <NA> <=2  <=4  <=4  <=20 <NA> <=4  <=2 
#>  [46] <NA> <=2  <=2  <=2  <=14 <NA> <=2  <=2  <=6  <NA> <=2  <=2  <=2  <=2  <NA>
#>  [61] <=2  <=2  <=4  <NA> <=2  <=2  <=2  <NA> <=2  <=2  <=4  <NA> <=6  <=6  <=6 
#>  [76] <=8  <NA> <=2  <=2  <=2  <=4  <NA> <=2  <=2  <=2  <NA> <=2  <=2  <=2  <=2 
#>  [91] <NA> <=2  <=2  <=2  <=2  <NA> <=2  <=2  <=12 <NA> <=2  <=2  <=2  <=8  <NA>
#> [106] <=2  <=2  <=2  <NA> <=2  <=2  <=4  <NA> <=2  <=4  <=8  <NA> <=2  <=2  <=2 
#> [121] <NA> <=2  <=2  <=2  <=4  <NA> <=2  <=2  <NA> <=2  <=2  <=2  <NA> <=2  <=2 
#> [136] <=4  <=4  <NA> <=2  <=2  <NA> <=2  <=4  <=4  <=2  <NA> <=6  <=10 <=16 <=24
#> [151] <NA> <=2  <=2  <=2  <=2  <NA> <=2  <=2  <=4  <=4  <NA> <=2  <=2  <=2  <NA>
#> [166] <=2  <=2  <=2  <NA> <=8  <=8  <=16 <=12 <NA> <=6  <=8  <=8  <=8  <NA> <=2 
#> [181] <=2  <=2  <=2  <NA> <=8  <=2  <=2  <NA> <=4  <=6  <=10 <=4  <NA> <=2  <=2 
#> [196] <=2  <=6  <NA> <=2  <=2  <=2  <NA> <=2  <=2  <=2  <NA> <=2  <=2  <NA> <=2 
#> [211] <=2  <=2  <=2  <NA> <=2  <=2  <NA> <=2  <=4  <=4  <=8  <NA> <=2  <=2  <=2 
#> [226] <=2  <NA> <=2  <=6  <=6  <=6  <NA> <=2  <=2  <=4  <NA> <=2  <=4  <=4  <NA>
#> [241] <=4  <=4  <NA> <=2  <=2  <=2  <NA> <=2  <=2  <=2  <=20 <NA> <=2  <=2  <NA>
#> [256] <=2  <=2  <=2  <NA> <=2  <=12 <=14 <=18 <NA> <=2  <=2  <=2  <=2  <NA> <=2 
#> [271] <=2  <NA> <=10 <=6  <=6  <NA> <=2  <=2  <=4  <=2  <NA> <=2  <=2  <=2  <NA>
#> [286] <=2  <=4  <=4  <=8  <NA> <=6  <=8  <=10 <NA> <=2  <NA> <=2  <=6  <NA> <=2 
#> [301] <=2  <=2  <=2  <NA> <=2  <=2  <=2  <NA> <=2  <=2  <=6  <NA> <=2  <=2  <=2 
#> [316] <NA> <=2  <=2  <NA> <=2  <=2  <=4  <=2  <NA> <=2  <=2  <=2  <=2  <NA> <=2 
#> [331] <=2  <=2  <NA> <=2  <=2  <=2  <NA> <=2  <=2  <=2  <=2  <NA> <=4  <=6  <=6 
#> [346] <NA> <=2  <=2  <=2  <=2  <NA> <=4  <=4  <=2  <NA> <=2  <=2  <=2  <NA> <=2 
#> [361] <=4  <NA> <=2  <=2  <=2  <=2  <NA> <=2  <=4  <=8  <NA> <=2  <=4  <=4  <NA>
#> [376] <=4  <=2  <=12 <NA> <=2  <=2  <=4  <=4  <NA> <=2  <=2  <=4  <NA> <=2  <=2 
#> [391] <=2  <NA> <=4  <=6  <NA> <=2  <=2  <=2  <NA> <=2  <=2  <=2  <NA> <=4  <=6 
#> [406] <NA> <=2  <=2  <=4  <NA> <=4  <=4  <=6  <NA> <=2  <=2  <=2  <=2  <NA> <=2 
#> [421] <=2  <=2  <=2  <NA> <=2  <=2  <=2  <=6  <NA> <=2  <=6  <=2  <=2  <NA> <=4 
#> [436] <=6  <=10 <=14 <NA> <=4  <=6  <=2  <=2  <NA> <=2  <=2  <=2  <=2  <NA> <=2 
#> [451] <=2  <=2  <NA> <=2  <=2  <=2  <NA> <=2  <=2  <=2  <NA> <=2  <=2  <=4  <=2 
#> [466] <NA> <=2  <=2  <=2  <=2  <NA> <=2  <=2  <=2  <=2  <NA> <=2  <=2  <=2  <NA>
#> [481] <=4  <=6  <=8  <NA> <=2  <=4  <NA> <=4  <=4  <NA> <=2  <=2  <=2  <NA> <=4 
#> [496] <=4  <=6  <=10 <NA> <=6  <=6  <=6  <NA> <=2  <=2  <=2  <=4  <NA> <=2  <=4 
#> [511] <NA> <=2  <=2  <NA> <=2  <=2  <=2  <=2  <NA> <=4  <=6  <NA> <=2  <=2  <=2 
#> [526] <NA> <=2  <=2  <=2  <NA> <=2  <=2  <=4  <=2  <NA> <=8  <=8  <=8  <=8  <NA>
#> [541] <=4  <=2  <NA> <=2  <=6  <=4  <NA> <=2  <=2  <=2  <NA> <=4  <=6  <=6  <NA>
#> [556] <=4  <=6  <=6  <NA> <=2  <=2  <=2  <=2  <NA> <=2  <=2  <=6  <NA> <=2  <=2 
#> [571] <=2  <NA> <=4  <=2  <NA> <=2  <=2  <=2  <NA> <=4  <=4  <=10 <=10 <NA> <=4 
#> [586] <=4  <NA> <=4  <=6  <=2  <=8  <NA> <=2  <=2  <NA> <=2  <=2  <NA> <=4  <=4 
#> [601] <=4  <NA> <=2  <=6  <=6  <NA> <=2  <=2  <=2  <=2  <NA> <=2  <=2  <NA> <=2 
#> [616] <=2  <=2  <=2  <NA> <=2  <=2  <=2  <NA> <=2  <=2  <NA> <=2  <=2  <=2  <NA>
#> [631] <=2  <=4  <=4  <NA> <=2  <=2  <NA> <=2  <=4  <=2  <=8  <NA> <=4  <=4  <=4 
#> [646] <NA> <=4  <=4  <=4  <NA> <=4  <=6  <=6  <NA> <=2  <=4  <NA> <=2  <=2  <NA>
#> [661] <=2  <=2  <=2  <=2  <NA> <=2  <=2  <=2  <=2  <NA> <=2  <=2  <=2  <NA> <=2 
#> [676] <=6  <NA> <=2  <NA> <=2  <=6  <NA> <=2  <=4  <=4  <NA> <=2  <=4  <=2  <NA>
#> [691] <=2  <=2  <NA> <=6  <=2  <NA> <=2  <=2  <=2  <=2  <NA> <=2  <=2  <=2  <NA>
#> [706] <=2  <=2  <=2  <=2  <NA> <=2  <=2  <NA> <=2  <=2  <=4  <NA> <=2  <=2  <=2 
#> [721] <=2  <NA> <=2  <=4  <=2  <=2  <NA> <=2  <=2  <NA> <=4  <=2  <NA> <=2  <=2 
#> [736] <=2  <=4  <NA> <=2  <=4  <=4  <=2  <NA> <=2  <=8  <=8  <=8  <NA> <=2  <=2 
#> [751] <NA> <=2  <=2  <NA> <=2  <=2  <NA> <=2  <=4  <NA> <=8  <=12 <=8  <NA> <=2 
#> [766] <=2  <=2  <=2  <NA> <=2  <=2  <=2  <=2  <NA> <=2  <=2  <=2  <NA> <=2  <=2 
#> [781] <=2  <NA> <=8  <=4  <NA> <=4  <=4  <=4  <=6  <NA> <=2  <=4  <=4  <NA> <=2 
#> [796] <=2  <=2  <NA> <=2  <=2  <NA> <=2  <=2  <=2  <=4  <NA> <=2  <=2  <NA> <=2 
#> [811] <=2  <=2  <NA> <=4  <=2  <=4  <=2  <NA> <=2  <=2  <=2  <NA> <=2  <=2  <=4 
#> [826] <NA> <=2  <=2  <NA> <=2  <=2  <=2  <NA> <=2  <=2  <NA> <=2  <=2  <NA> <=2 
#> [841] <=2  <NA> <=2  <=2  <NA> <=2  <=2  <NA> <=4  <=4  <NA> <=2  <=2  <NA> <=2 
#> [856] <=2  <=2  <NA> <=2  <=2  <=2  <NA> <=2  <=2  <NA> <=2  <=4  <=4  <NA> <=2 
#> [871] <=2  <=2  <NA> <=2  <=4  <NA> <=2  <=2  <=2  <NA> <=2  <=2  <=2  <=2  <NA>
#> [886] <=2  <=2  <NA> <=2  <=2  <=2  <=2  <NA> <=2  <=2  <=2  <NA> <=2  <=2  <=2 
#> [901] <NA> <=6  <=2  <NA> <=2  <=2  <NA> <=2  <=2  <=2  <NA> <=2  <=2  <=2  <NA>
#> [916] <=2  <=2  <=2  <=4  <NA> <=4  <=4  <=6  <=6  <NA> <=2  <=2  <=2  <=2  <NA>
#> [931] <=2  <=2  <NA> <=2  <=2  <=2  <=2  <NA> <=2  <=2  <NA> <=2  <=2  <=2  <=2 
#> 15 Levels: <=2 < <=4 < <=6 < <=8 < <=10 < <=12 < <=14 < <=16 < ... < <=30

  # Previous test result as column of data frame
(Blackmore <- add_prev_result(Blackmore)) |> head(32)
#>    subject   age exercise   group  timepoint result prev_result
#> 1      100  8.00     2.71 patient 2008-01-01    <=4        <NA>
#> 2      100 10.00     1.94 patient 2009-12-31    <=2         <=4
#> 3      100 12.00     2.36 patient 2012-01-01    <=4         <=2
#> 4      100 14.00     1.54 patient 2014-01-01    <=2         <=4
#> 5      100 15.92     8.63 patient 2015-12-03   <=10         <=2
#> 6      101  8.00     0.14 patient 2008-01-01    <=2        <NA>
#> 7      101 10.00     0.14 patient 2009-12-31    <=2         <=2
#> 8      101 12.00     0.00 patient 2012-01-01    <=2         <=2
#> 9      101 14.00     0.00 patient 2014-01-01    <=2         <=2
#> 10     101 16.67     5.08 patient 2016-09-02    <=6         <=2
#> 11     102  8.00     0.92 patient 2008-01-01    <=2        <NA>
#> 12     102 10.00     1.82 patient 2009-12-31    <=2         <=2
#> 13     102 12.00     4.75 patient 2012-01-01    <=6         <=2
#> 14     102 15.08    24.72 patient 2015-01-30   <=26         <=6
#> 15     103  8.00     1.04 patient 2008-01-01    <=2        <NA>
#> 16     103 10.00     2.90 patient 2009-12-31    <=4         <=2
#> 17     103 12.00     2.65 patient 2012-01-01    <=4         <=4
#> 18     103 14.08     6.86 patient 2014-01-30    <=8         <=4
#> 19     104  8.00     2.75 patient 2008-01-01    <=4        <NA>
#> 20     104 10.00     6.62 patient 2009-12-31    <=8         <=4
#> 21     104 12.00     0.29 patient 2012-01-01    <=2         <=8
#> 22     104 15.42    12.37 patient 2015-06-03   <=14         <=2
#> 23     105  8.00     0.05 patient 2008-01-01    <=2        <NA>
#> 24     105 10.00     0.00 patient 2009-12-31    <=2         <=2
#> 25     105 12.00     0.00 patient 2012-01-01    <=2         <=2
#> 26     105 14.00     0.25 patient 2014-01-01    <=2         <=2
#> 27     105 16.17     1.44 patient 2016-03-03    <=2         <=2
#> 28     106  8.00     0.00 patient 2008-01-01    <=2        <NA>
#> 29     106 10.00     0.46 patient 2009-12-31    <=2         <=2
#> 30     106 12.00     0.12 patient 2012-01-01    <=2         <=2
#> 31     106 14.00     1.34 patient 2014-01-01    <=2         <=2
#> 32     106 16.33     4.83 patient 2016-05-01    <=6         <=2

rm(Blackmore)