9.4 Constant Variables

20200814 You may wish and typically do ignore variables (dataset columns) with constant values as they add no extra information to the analysis.

# Identify variables that have a single value.

ds %>%
  select(all_of(vars)) %>%
  sapply(function(x) all(x == x[1L])) %>%
  which() %>%
  names() %T>%
  print() ->
constants

## character(0)

If you are accumulating a list of variables to ignore then add these constants to that list.

# Add to the variables to be ignored for modelling.

ignore %<>% union(constants)

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