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DanishSnowballStemmer.Stem

The Snowball stem of one Danish word.

public static string Stem(string word)

Parameters — word is a single Danish word. It is lowercased and NFC-normalised before the rules run, so a decomposed æ and a composed one are the same letter to the algorithm.

Returns — string, the stem, always lowercase, and still carrying whatever æ, å or ø the input had.

Exceptions — ArgumentNullException when word is null. An empty string, or a word of one character, is returned lowercased and otherwise untouched.

Example — a derived adjective stripped, and one rewritten rather than stripped.

using Lodestar.Text.Stemming;

string noun = DanishSnowballStemmer.Stem("kærlighed");  // => kær
string genitive = DanishSnowballStemmer.Stem("kærlighedens");  // => kær
string adjective = DanishSnowballStemmer.Stem("hjælpeløst");  // => hjælpeløs

Remarks — kærlighed → kær is the result most likely to look like a bug. It is not: hed is one of the endings the first step removes, lig is one of the four the third step removes, and the algorithm has no dictionary to tell it that what remains happens to be another word. A stemmer produces keys, not words, and kærlighed, kærlig and kærligt all reaching kær is the point of it.

The superlative is the other one worth knowing. A word ending igst loses the st before the third step's suffix search runs at all, which is what puts a superlative and its positive on one key — and the consonant-pair step then removes a gt or a kt inside R1, which does the same for a neuter form.

using Lodestar.Text.Stemming;

string superlative = DanishSnowballStemmer.Stem("hurtigst");  // => hurt
string positive = DanishSnowballStemmer.Stem("hurtigt");  // => hurt
string neuter = DanishSnowballStemmer.Stem("friskt");  // => frisk

Applies to — net10.0, netstandard2.0.

See also — DanishSnowballStemmer, the stemming index.