withRowsSampled method

DataFrame withRowsSampled(int n, { bool withReplacement = false, int? seed, })

A new data frame comprising sampled rows.

Example:

print(iris.withHead(3));
print(iris.withHead(3).withRowsSampled(
  5, withReplacement: true, seed: 0));

.--.------------.-----------.------------.-----------.--------.
|id|sepal_length|sepal_width|petal_length|petal_width|species |
:--+------------+-----------+------------+-----------+--------:
|1 |5.1         |3.5        |1.4         |0.2        |setosa  |
|2 |4.9         |3.0        |1.4         |0.2        |setosa  |
|3 |4.7         |3.2        |1.3         |0.2        |setosa  |
'--'------------'-----------'------------'-----------'--------'

.--.------------.-----------.------------.-----------.--------.
|id|sepal_length|sepal_width|petal_length|petal_width|species |
:--+------------+-----------+------------+-----------+--------:
|1 |5.1         |3.5        |1.4         |0.2        |setosa  |
|3 |4.7         |3.2        |1.3         |0.2        |setosa  |
|2 |4.9         |3.0        |1.4         |0.2        |setosa  |
|2 |4.9         |3.0        |1.4         |0.2        |setosa  |
|1 |5.1         |3.5        |1.4         |0.2        |setosa  |
'--'------------'-----------'------------'-----------'--------'

Implementation

DataFrame withRowsSampled(
  int n, {
  bool withReplacement = false,
  int? seed,
}) {
  final rand = math.Random(seed);
  if (withReplacement) {
    return withRowsAtIndices(
        [for (var _ = 0; _ < n; _++) rand.nextInt(rowNumber)]);
  }
  if (n > rowNumber) {
    throw PackhorseError.badArgument("Cannot sample $n rows from $rowNumber "
        "(DataFrame.withRowsSampled).");
  }
  return withRowsAtIndices(
      ([for (var i = 0; i < rowNumber; i++) i]..shuffle(rand)).sublist(n));
}