make_knn_strata {nncc}

Make case-control strata using k nearest neighbors (knn)

Description

Select a pre-defined number of controls for each case based on calculated distances between cases and controls.

Usage

make_knn_strata(
  expvar,
  matchvars,
  df,
  rmvars = data.frame(exp_var = character(), rm_vars = character(), stringsAsFactors =
    FALSE),
  casevar = "case",
  ncntls = 250,
  metric = "gower",
  silent = FALSE
)

Arguments

expvar

A character - the name of the exposure variable in df.

matchvars

Character vector - what are the variables to match on. Note that the function automatically excludes the the exposure variable.

df

A dataframe that contains the case-control data.

rmvars

A data frame that lists variables to be excluded from matching for each exposure. For details, please see the vignette of this package.

casevar

A character - what is the name of the variable indicating case status (1 = case, 0 = control)

ncntls

An integer to specify number of controls to find for each case (k in knn).

metric

A character to specify a metric for measuring distance between a case and a control. See daisy.

silent

Suppress exposure info useful for *apply/loop implementations?

Details

For more information, please refer to the vignette using browseVignettes("nncc").

Value

A list of data frames with a length of number of exposures of interest.