The initial data.frame with new columns for each numeric variable included with a value of 0 if not an outlier and 1 if that row is an outlier.
Arguments
data
A data.frame
select_columns
A string or vector of strings with the name(s) of the numeric columns to check
for outliers. If NULL (default), will use all numeric columns in the data.
group_variable
A string with the name of the column with the grouping variable.
std_dev_value
A number indicating how many standard deviations away from the mean to
determine if a value is an outlier.
zero_is_outlier
If TRUE (not default), reports any zero value as an outlier.