withCategoricColumnFromFormula method

DataFrame withCategoricColumnFromFormula({
  1. required String name,
  2. required String formula,
  3. required String generator(
    1. num
    ),
})

A new data frame with a categoric column generated from a formula.

Example:

print(petals.withHead(5));
print(petals.withHead(5).withCategoricColumnFromFormula(
  name: "geom_mean",
  formula: "sqrt(petal_width * petal_length)",
  generator: (result) => result > 1 ? "large" : "small"
));


.--.------------.-----------.------------.
|id|petal_length|petal_width|species     |
:--+------------+-----------+------------:
|1 |1.4         |0.2        |setosa      |
|2 |1.4         |0.2        |setosa      |
|3 |1.3         |0.2        |setosa      |
|4 |1.5         |0.2        |setosa      |
|51|4.7         |1.4        |versicolor  |
'--'------------'-----------'------------'

.--.------------.-----------.------------.---------.
|id|petal_length|petal_width|species     |geom_mean|
:--+------------+-----------+------------+---------:
|1 |1.4         |0.2        |setosa      |small    |
|2 |1.4         |0.2        |setosa      |small    |
|3 |1.3         |0.2        |setosa      |small    |
|4 |1.5         |0.2        |setosa      |small    |
|51|4.7         |1.4        |versicolor  |large    |
'--'------------'-----------'------------'---------'

Implementation

DataFrame withCategoricColumnFromFormula({
  required String name,
  required String formula,
  required String Function(num) generator,
}) {
  if (!_columnNameOkay(name)) {
    throw PackhorseError.badColumnName(name);
  }
  return copy
    ..categoricColumns[name] =
        CategoricColumn(_formulaResults(formula).map(generator));
}