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Fuzz.Ratio

Edit-distance similarity over the whole of both strings.

public static double Ratio(string a, string b)

public static double Ratio(string a, string b, TextElement element)

The second overload compares over element. At TextElement.CodePoint a character outside the Basic Multilingual Plane counts once, tokens split on rapidfuzz's own whitespace and sort by code point, which is rapidfuzz's score on any string; TextElement.Utf16Unit is the first overload.

Parameters — a and b are the strings to compare. Order does not change the answer. element is the unit compared, in the second overload only.

Returns — double in [0, 100]. 100 when identical, 0 when they share nothing.

Exceptions — ArgumentOutOfRangeException when element is not a declared value. This scorer has no upper bound on the alphabet: past the 63,455 code points a char can rank it compares the code points themselves.

Example — a transposition, and the two extremes.

using Lodestar.Fuzzy;

double typo = Fuzz.Ratio("apple pie", "appel pie");  // => 88.88888888888889
double same = Fuzz.Ratio("abc", "abc");  // => 100
double nothing = Fuzz.Ratio("abc", "xyz");  // => 0

The same call over code points, on two emoji that share their high surrogate.

using Lodestar.Fuzzy;
using Lodestar.Text;

double units = Fuzz.Ratio("\U0001F600", "\U0001F601");                           // => 50
double codePoints = Fuzz.Ratio("\U0001F600", "\U0001F601", TextElement.CodePoint);  // => 0

Remarks — this is the scorer to reach for when the two strings are the same kind of thing: two spellings of a name, two renderings of an address. It compares everything, which is its strength and its limit.

Length is what breaks it. Fuzz.Ratio("apple", "an apple a day") is low, not because the strings disagree but because most of the second is absent from the first — and PartialRatio is the answer to that shape.

An emoji is two UTF-16 units, so the first overload scores two different emoji that share a high surrogate as half alike, where rapidfuzz scores them 0; pass TextElement.CodePoint when the text can leave the BMP, as decision 0001 offers on every algorithm it affects.

Applies to — net10.0, netstandard2.0.

See also — Fuzz.PartialRatio, Fuzz.TokenSortRatio.