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ImputationStrategy

What SimpleImputer fills a missing value with.

public enum ImputationStrategy

Fields — Mean (the default, as the reference's is), Median, MostFrequent and Constant — strategy="mean", "median", "most_frequent" and "constant".

Example — the tie rule, which is the one worth knowing.

using Lodestar.Preprocessing;

// 1 and 2 both appear twice.
double[] tied = [1.0, 1.0, 2.0, 2.0, double.NaN];

SimpleImputer imputer = SimpleImputer.Fit(
    tied, 1, new SimpleImputerOptions { Strategy = ImputationStrategy.MostFrequent });

double fill = imputer.Statistics[0];  // => 1

Remarks — a tie goes to the smaller value, measured against the reference rather than assumed. An implementation that keeps the last of an equally long run fills with 2 instead and passes every untied case, which is why the corpus freezes this one.

Median is numpy.median: for an even count, the average of the two middle values.

Applies to — net10.0, netstandard2.0.

See also — SimpleImputerOptions, SimpleImputer.Fit.