Test-Retest Reliability — compute

Uses the ICC() function in the psych package to compute the ICC(2,1) on a stable subset of subjects. Note that this is equivalent to the ICC(A,1) See Intraclass correlation – A discussion and demonstration of basic features by Liljequist et al 2019. Also see documentation of the psych package.

compute_icc21(
  dat,
  PRO.score = NULL,
  time.var = NULL,
  subject.id = NULL,
  anchor = NULL,
  stable.score = NULL,
  first.timepoint = NULL,
  second.timepoint = NULL
)

Arguments

dat	dataframe with values
PRO.score	specify the COA/PRO score you want to compute ICC of. Can pass multiple scores, e.g. `PRO.score = c('Y_comp', 'Y_mcar', 'Y_mar')`
time.var	the time variable, should be an ordered factor
subject.id	the subject ID, should be a character variable
anchor	this is the anchor used to condition on the stable subset of subjects
stable.score	this is the anchor score that indicates the subject is stable. For example, use `anchor = 'PGIS_delta'` and `stable.score = 0` to select the subset of stable sujects. Another example would be `anchor = 'anchor.groups'` and `stable.score = 'Maintained'`.
first.timepoint	specify the first timepoint to be used in the TRTR computation; default is the first timepoint in your `time.var` variable
second.timepoint	specifiy the second timepoint to be used in the TRTR computation; default is the final timepoint in your `time.var` variable

Value

returns a table icc.21 with the values