Porter stemming is designed for the English language.

Description

Demo Code


/**//from ww w . jav a2  s .c  o  m
 * 18 May 2008
 * Stemming is the process for reducing inflected (or sometimes derived) words to their stem, base or root
 * form. Porter stemming is designed for the English language.
 * 
 * This code has been slighly adapted from Martin Porter's examples.
 *  - http://tartarus.org/~martin/PorterStemmer/
 *  
 * Please assume any errors found in the below code are translation errors
 * inserted by myself and not those of the original authors.
 *  
 * @author Matt Chadburn <matt@commuterjoy.co.uk>
 */
String.prototype.porterStemmer = function(){
  

  step2list = new Array();
  step2list["ational"]="ate";
  step2list["tional"]="tion";
  step2list["enci"]="ence";
  step2list["anci"]="ance";
  step2list["izer"]="ize";
  step2list["bli"]="ble";
  step2list["alli"]="al";
  step2list["entli"]="ent";
  step2list["eli"]="e";
  step2list["ousli"]="ous";
  step2list["ization"]="ize";
  step2list["ation"]="ate";
  step2list["ator"]="ate";
  step2list["alism"]="al";
  step2list["iveness"]="ive";
  step2list["fulness"]="ful";
  step2list["ousness"]="ous";
  step2list["aliti"]="al";
  step2list["iviti"]="ive";
  step2list["biliti"]="ble";
  step2list["logi"]="log";
  
  step3list = new Array();
  step3list["icate"]="ic";
  step3list["ative"]="";
  step3list["alize"]="al";
  step3list["iciti"]="ic";
  step3list["ical"]="ic";
  step3list["ful"]="";
  step3list["ness"]="";

  c = "[^aeiou]";          // consonant
  v = "[aeiouy]";          // vowel
  C = c + "[^aeiouy]*";    // consonant sequence
  V = v + "[aeiou]*";      // vowel sequence
  
  mgr0 = "^(" + C + ")?" + V + C;               // [C]VC... is m>0
  meq1 = "^(" + C + ")?" + V + C + "(" + V + ")?$";  // [C]VC[V] is m=1
  mgr1 = "^(" + C + ")?" + V + C + V + C;       // [C]VCVC... is m>1
  s_v   = "^(" + C + ")?" + v;                   // vowel in stem

  var stem;
  var suffix;
  var firstch;
  var origword = this;
  var w = this;
  
  if (this.length < 3) { return this; }

     var re;
     var re2;
     var re3;
     var re4;

  firstch = this.substr(0,1);
  if (firstch == "y") {
    w = firstch.toUpperCase() + w.substr(1);
  }

  // Step 1a
     re = /^(.+?)(ss|i)es$/;
     re2 = /^(.+?)([])s$/;

     if (re.test(w)) { w = w.replace(re,"$1$2"); }
     else if (re2.test(w)) {  w = w.replace(re2,"$1$2"); }

  // Step 1b
  re = /^(.+?)eed$/;
  re2 = /^(.+?)(ed|ing)$/;
  if (re.test(w)) {
    var fp = re.exec(w);
    re = new RegExp(mgr0);
    if (re.test(fp[1])) {
      re = /.$/;
      w = w.replace(re,"");
    }
  } else if (re2.test(w)) {
    var fp = re2.exec(w);
    stem = fp[1];
    re2 = new RegExp(s_v);
    if (re2.test(stem)) {
      w = stem;
      re2 = /(at|bl|iz)$/;
      re3 = new RegExp("([^aeiouylsz])\\1$");
      re4 = new RegExp("^" + C + v + "[^aeiouwxy]$");
      if (re2.test(w)) {  w = w + "e"; }
      else if (re3.test(w)) { re = /.$/; w = w.replace(re,""); }
      else if (re4.test(w)) { w = w + "e"; }
    }
  }

  // Step 1c
  re = /^(.+?)y$/;
  if (re.test(w)) {
    var fp = re.exec(w);
    stem = fp[1];
    re = new RegExp(s_v);
    if (re.test(stem)) { w = stem + "i"; }
  }

  // Step 2
  re = /^(.+?)(ational|tional|enci|anci|izer|bli|alli|entli|eli|ousli|ization|ation|ator|alism|iveness|fulness|ousness|aliti|iviti|biliti|logi)$/;
  if (re.test(w)) {
    var fp = re.exec(w);
    stem = fp[1];
    suffix = fp[2];
    re = new RegExp(mgr0);
    if (re.test(stem)) {
      w = stem + step2list[suffix];
    }
  }

  // Step 3
  re = /^(.+?)(icate|ative|alize|iciti|ical|ful|ness)$/;
  if (re.test(w)) {
    var fp = re.exec(w);
    stem = fp[1];
    suffix = fp[2];
    re = new RegExp(mgr0);
    if (re.test(stem)) {
      w = stem + step3list[suffix];
    }
  }

  // Step 4
  re = /^(.+?)(al|ance|ence|er|ic|able|ible|ant|ement|ment|ent|ou|ism|ate|iti|ous|ive|ize)$/;
  re2 = /^(.+?)(s|t)(ion)$/;
  if (re.test(w)) {
    var fp = re.exec(w);
    stem = fp[1];
    re = new RegExp(mgr1);
    if (re.test(stem)) {
      w = stem;
    }
  } else if (re2.test(w)) {
    var fp = re2.exec(w);
    stem = fp[1] + fp[2];
    re2 = new RegExp(mgr1);
    if (re2.test(stem)) {
      w = stem;
    }
  }

  // Step 5
  re = /^(.+?)e$/;
  if (re.test(w)) {
    var fp = re.exec(w);
    stem = fp[1];
    re = new RegExp(mgr1);
    re2 = new RegExp(meq1);
    re3 = new RegExp("^" + C + v + "[^aeiouwxy]$");
    if (re.test(stem) || (re2.test(stem) && !(re3.test(stem)))) {
      w = stem;
    }
  }

  re = /ll$/;
  re2 = new RegExp(mgr1);
  if (re.test(w) && re2.test(w)) {
    re = /.$/;
    w = w.replace(re,"");
  }

  // and turn initial Y back to y

  if (firstch == "y") {
    w = firstch.toLowerCase() + w.substr(1);
  }

  return w;

}
Porter stemming is designed for the English language. - Node.js String

Description

Demo Code

Related Tutorials
