#ml #учеба  [[data mining]]
![[Pasted image 20260719174012.png]]

Main function to reduce word to it's original (root) form - stem (lemma).
### Lovins stemmer 
Rules only, remove suffixes, main problem is over removal of suffixes the, those, them - the, love - lov and so on.
### Porter stemmer
Classify characters as vowels and consonant. Group sequential v and c and remove them by some rules (have rules, so still have some errors)  Implementation in nltk. 
### Snowball stemmer 
Updated porter with new rules, stop word and including other languages (including Russian) also have stop words list, such as  _the_, _a_, _being_, and the like. Also has implementation in nltk.


Source: https://www.ibm.com/think/topics/stemming?regionCode=us&languageCode=en&cm-history=us-en