Metrics undefinedmetricexception

Development build. This page describes main, not a released package. The latest published Lodestar.Metrics is 0.3.0 — read its documentation.

UndefinedMetricException

Thrown when a metric has no value and you asked to be told rather than handed a number.

public sealed class UndefinedMetricException : InvalidOperationException

Constructors — the parameterless one carries a default message; the others take a message, and a message with an inner exception.

Example — asking to be told instead of scoring 0.

using Lodestar.Metrics;

int[] yTrue = [0, 0, 1];
int[] yPred = [0, 0, 0];

string what = "nothing was thrown";
try
{
    _ = Precision.Score(yTrue, yPred, zeroDivision: ZeroDivision.Throw);
}
catch (UndefinedMetricException error)
{
    what = error.Message;
}

string message = what;   // => Precision is undefined here: no sample contributes…

Remarks — this is the counterpart of scikit-learn's UndefinedMetricWarning, which it does not reproduce and deliberately improves on. A warning in Python is easy to miss and easy to filter, and the value that comes back with it — 0.0 — is indistinguishable in a report from a genuinely terrible score. Selecting ZeroDivision.Throw turns that silence into a stack trace naming the metric.

The trap is reaching for it as the default. It is not, and should not be: parity with scikit-learn requires the value, so ZeroDivision.Zero is what every precision-family metric starts from. Throw is the setting for a pipeline that would rather fail than publish a number nobody can interpret — which is a reasonable thing to want in CI and a bad thing to want in a dashboard.

Applies to — net10.0, netstandard2.0.

See also — ZeroDivision, Precision.Score, CohenKappa.Score, the Python equivalence table.

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