Flag univariate and multivariate outliers — outlier

Uses transparent screening rules for numeric survey response variables. The report supports data review before modelling, not automatic deletion.

Usage

outlier_report(
  data,
  variables = NULL,
  method = c("zscore", "iqr", "mahalanobis"),
  z_cut = 3,
  iqr_multiplier = 1.5,
  p_cut = 0.975
)

Arguments

data: A data.frame.
variables: Character vector of numeric variables to screen. When NULL, all numeric columns are used.
method: Outlier rule. "zscore" flags absolute z scores above z_cut; "iqr" flags values outside Tukey fences; "mahalanobis" flags rows above the chi-square cutoff for the selected variables.
z_cut: Numeric cutoff for "zscore". Defaults to 3.
iqr_multiplier: Numeric multiplier for "iqr" fences. Defaults to 1.5.
p_cut: Probability cutoff for "mahalanobis". Defaults to 0.975.

Value

An object of class sframe_outlier_report with the method, screened variables, a result table, flagged row numbers, and a reporting prompt.

Examples

demo <- sframe_demo_data()
outliers <- outlier_report(
  demo$responses,
  variables = c("dm_1", "dm_2", "sat_1"),
  method = "zscore"
)
outliers$flagged_rows
#> integer(0)