Text 0.3.2 ratcliffobershelp distance

Lodestar.Text 0.3.2. This page is frozen at that release. Read the current documentation for what main says now. A link to a decision or a migration page follows main, and leaves the archive.

RatcliffObershelp.Distance

1 - Similarity, for code that wants a distance rather than a score.

public static double Distance(ReadOnlySpan<char> a, ReadOnlySpan<char> b, TextElement element = TextElement.Utf16Unit)

Parameters — a and b are the two strings to compare; element says what counts as one character, exactly as it does for Similarity, which this subtracts from 1.

Returns — double in [0, 1], larger meaning less alike. 0 for equal inputs, and 0 when both are empty.

Example — the share of the two strings their matched blocks fail to cover.

using Lodestar.Text.Distances;

double d = RatcliffObershelp.Distance("state", "taste");   // => 0.4

Remarks — the same measure turned round, for code that sorts ascending or thresholds with "at most". It carries no information Similarity does not.

The trap is the empty case landing opposite to Jaro.Distance: two empty strings are 1 similar here and therefore 0 apart, where Jaro.Distance("", "") is 1. Two blank fields are the closest possible pair under this measure and the furthest under that one, which is worth pinning down before either is used to rank records.

Applies to — net10.0, netstandard2.0.

See also — RatcliffObershelp.Similarity, Jaro.Distance, decision 0006, the Python equivalence table.