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Repeats shuffled stratified k-fold, as RepeatedStratifiedKFold does.

public static IReadOnlyList<FoldSplit> RepeatedStratifiedKFold(ReadOnlySpan<int> labels, int foldCount, int repeatCount, long randomState)

Parameters — labels is one class label per row. foldCount is how many folds each repeat cuts. repeatCount is how many repeats, at least one. randomState is scikit-learn's random_state, in [0, 2³² − 1].

Returns — repeatCount · foldCount folds, repeat by repeat, each index list ascending.

Exceptions — ArgumentOutOfRangeException when a count or randomState is out of range. ArgumentException when foldCount is above every class's count. ArgumentException also when the folds times the classes are more cells than one array holds (#1314). ArgumentException also when the repeats times the folds are more splits than one list holds (#1318).

Example — twelve rows in three classes, three folds, two repeats.

using Lodestar.Preprocessing;

int[] labels = [0, 0, 0, 0, 0, 0, 1, 1, 1, 2, 2, 2];

IReadOnlyList<FoldSplit> folds = Splitters.RepeatedStratifiedKFold(labels, foldCount: 3, repeatCount: 2, randomState: 0);

int count = folds.Count;                                        // => 6
string first = string.Join(",", folds[0].TestIndices);          // => 2,4,7,11
string fourth = string.Join(",", folds[3].TestIndices);         // => 1,5,6,10

Remarks — each repeat is Splitters.StratifiedKFold with a seed, drawing from the one generator the repeats share.

Applies to — net10.0, netstandard2.0.

See also — Splitters.RepeatedKFold, Splitters.StratifiedKFold.