/*
* JGAAP -- a graphical program for stylometric authorship attribution
* Copyright (C) 2009,2011 by Patrick Juola
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/**
**/
package com.jgaap.eventDrivers;
import com.jgaap.backend.API;
import com.jgaap.util.Event;
import com.jgaap.util.EventSet;
/**
* Applies Porter's stemming algorithm (the Porter Stemmer) to produce just the
* stems of the underlying words or word sets.
*
* Stems, e.g. : farms, farmed, farming should all become just "farm"
*
* Porter's algorithm is freely licenced for all uses; I got the code from
* Martin Porter himself at http://tartarus.org/~martin/PorterStemmer/java.txt
*
* A few comments: 1) This algorithm is (obviously) English-only 2) There are
* better stemming algorithms out there (TODO) such as the Snowball algorithm.
* 3) The code only works for lower case characters. Should not be a problem
* most of the time. I have put in an ugly hack to address. 4) Ditto
* punctuation. I have NOT put in a hack to address
*/
public class PorterStemmerEventDriver extends NaiveWordEventDriver {
@Override
public String displayName() {
return "Word stems";
}
@Override
public String tooltipText() {
return "Word stems derived from the Porter stemmer (English only)";
}
@Override
public boolean showInGUI() {
// only valid for English documents
return API.getInstance().getLanguage().getLanguage().equalsIgnoreCase("english");
}
/**
* Creates EventSet using Porter stemmer on underlying events
*/
@Override
public EventSet createEventSet(char[] text) {
EventSet raw = super.createEventSet(text);
EventSet cooked = new EventSet();
Stemmer theStemmer = new Stemmer();
String r, s;
char[] a, b;
// stem each "Event" in the set
for (int i = 0; i < raw.size(); i++) {
// convert event to (lower case) character array
r = raw.eventAt(i).toString();
s = r.toLowerCase();
a = s.toCharArray();
// process via Stemmer
theStemmer.add(a, s.length());
theStemmer.stem();
b = theStemmer.getResultBuffer();
// and hack original case pattern
for (int ii = 0; ii < theStemmer.getResultLength(); ii++)
if (Character.isUpperCase(r.charAt(ii))) {
b[ii] = Character.toUpperCase(b[ii]);
}
// and, finally, add result to new EventSet
cooked.addEvent(new Event(new String(b, 0, theStemmer
.getResultLength()), this));
}
return cooked;
}
// Martin Porter's code (slightly changed) starts here. (PMJ)
// N.b. "Stemmer" class is changed to private so as to not mess stuff up.
// DO NOT MESS WITH STUFF BELOW THIS LINE UNLESS YOU ARE WILLING TO RETEST
// ON THE 20,000 WORD VOCABULARY!
/*
*
* Porter stemmer in Java. The original paper is in
*
* Porter, 1980, An algorithm for suffix stripping, Program, Vol. 14, no. 3,
* pp 130-137,
*
* See also http://www.tartarus.org/~martin/PorterStemmer
*
* History:
*
* Release 1
*
* Bug 1 (reported by Gonzalo Parra 16/10/99) fixed as marked below. The
* words 'aed', 'eed', 'oed' leave k at 'a' for step 3, and b[k-1] is then
* out outside the bounds of b.
*
* Release 2
*
* Similarly,
*
* Bug 2 (reported by Steve Dyrdahl 22/2/00) fixed as marked below. 'ion' by
* itself leaves j = -1 in the test for 'ion' in step 5, and b[j] is then
* outside the bounds of b.
*
* Release 3
*
* Considerably revised 4/9/00 in the light of many helpful suggestions from
* Brian Goetz of Quiotix Corporation (brian@quiotix.com).
*
* Release 4
*/
/**
* Stemmer, implementing the Porter Stemming Algorithm
*
* The Stemmer class transforms a word into its root form. The input word
* can be provided a character at time (by calling add()), or at once by
* calling one of the various stem(something) methods.
*/
@SuppressWarnings("unused")
private class Stemmer {
private char[] b;
private int i, /* offset into b */
i_end, /* offset to end of stemmed word */
j, k;
private static final int INC = 50;
/* unit of size whereby b is increased */
public Stemmer() {
b = new char[INC];
i = 0;
i_end = 0;
}
/**
* Add a character to the word being stemmed. When you are finished
* adding characters, you can call stem(void) to stem the word.
*/
public void add(char ch) {
if (i == b.length) {
char[] new_b = new char[i + INC];
for (int c = 0; c < i; c++)
new_b[c] = b[c];
b = new_b;
}
b[i++] = ch;
}
/**
* Adds wLen characters to the word being stemmed contained in a portion
* of a char[] array. This is like repeated calls of add(char ch), but
* faster.
*/
public void add(char[] w, int wLen) {
if (i + wLen >= b.length) {
char[] new_b = new char[i + wLen + INC];
for (int c = 0; c < i; c++)
new_b[c] = b[c];
b = new_b;
}
for (int c = 0; c < wLen; c++)
b[i++] = w[c];
}
/**
* After a word has been stemmed, it can be retrieved by toString(), or
* a reference to the internal buffer can be retrieved by
* getResultBuffer and getResultLength (which is generally more
* efficient.)
*/
public String toString() {
return new String(b, 0, i_end);
}
/**
* Returns the length of the word resulting from the stemming process.
*/
public int getResultLength() {
return i_end;
}
/**
* Returns a reference to a character buffer containing the results of
* the stemming process. You also need to consult getResultLength() to
* determine the length of the result.
*/
public char[] getResultBuffer() {
return b;
}
/* cons(i) is true <=> b[i] is a consonant. */
private final boolean cons(int i) {
switch (b[i]) {
case 'a':
case 'e':
case 'i':
case 'o':
case 'u':
return false;
case 'y':
return (i == 0) ? true : !cons(i - 1);
default:
return true;
}
}
/*
* m() measures the number of consonant sequences between 0 and j. if c
* is a consonant sequence and v a vowel sequence, and <..> indicates
* arbitrary presence,
*
* <c><v> gives 0 <c>vc<v> gives 1 <c>vcvc<v> gives 2 <c>vcvcvc<v> gives
* 3 ....
*/
private final int m() {
int n = 0;
int i = 0;
while (true) {
if (i > j)
return n;
if (!cons(i))
break;
i++;
}
i++;
while (true) {
while (true) {
if (i > j)
return n;
if (cons(i))
break;
i++;
}
i++;
n++;
while (true) {
if (i > j)
return n;
if (!cons(i))
break;
i++;
}
i++;
}
}
/* vowelinstem() is true <=> 0,...j contains a vowel */
private final boolean vowelinstem() {
int i;
for (i = 0; i <= j; i++)
if (!cons(i))
return true;
return false;
}
/* doublec(j) is true <=> j,(j-1) contain a double consonant. */
private final boolean doublec(int j) {
if (j < 1)
return false;
if (b[j] != b[j - 1])
return false;
return cons(j);
}
/*
* cvc(i) is true <=> i-2,i-1,i has the form consonant - vowel -
* consonant and also if the second c is not w,x or y. this is used when
* trying to restore an e at the end of a short word. e.g.
*
* cav(e), lov(e), hop(e), crim(e), but snow, box, tray.
*/
private final boolean cvc(int i) {
if (i < 2 || !cons(i) || cons(i - 1) || !cons(i - 2))
return false;
{
int ch = b[i];
if (ch == 'w' || ch == 'x' || ch == 'y')
return false;
}
return true;
}
private final boolean ends(String s) {
int l = s.length();
int o = k - l + 1;
if (o < 0)
return false;
for (int i = 0; i < l; i++)
if (b[o + i] != s.charAt(i))
return false;
j = k - l;
return true;
}
/*
* setto(s) sets (j+1),...k to the characters in the string s,
* readjusting k.
*/
private final void setto(String s) {
int l = s.length();
int o = j + 1;
for (int i = 0; i < l; i++)
b[o + i] = s.charAt(i);
k = j + l;
}
/* r(s) is used further down. */
private final void r(String s) {
if (m() > 0)
setto(s);
}
/*
* step1() gets rid of plurals and -ed or -ing. e.g.
*
* caresses -> caress ponies -> poni ties -> ti caress -> caress cats ->
* cat
*
* feed -> feed agreed -> agree disabled -> disable
*
* matting -> mat mating -> mate meeting -> meet milling -> mill messing
* -> mess
*
* meetings -> meet
*/
private final void step1() {
if (b[k] == 's') {
if (ends("sses"))
k -= 2;
else if (ends("ies"))
setto("i");
else if (b[k - 1] != 's')
k--;
}
if (ends("eed")) {
if (m() > 0)
k--;
} else if ((ends("ed") || ends("ing")) && vowelinstem()) {
k = j;
if (ends("at"))
setto("ate");
else if (ends("bl"))
setto("ble");
else if (ends("iz"))
setto("ize");
else if (doublec(k)) {
k--;
{
int ch = b[k];
if (ch == 'l' || ch == 's' || ch == 'z')
k++;
}
} else if (m() == 1 && cvc(k))
setto("e");
}
}
/*
* step2() turns terminal y to i when there is another vowel in the
* stem.
*/
private final void step2() {
if (ends("y") && vowelinstem())
b[k] = 'i';
}
/*
* step3() maps double suffices to single ones. so -ization ( = -ize
* plus -ation) maps to -ize etc. note that the string before the suffix
* must give m() > 0.
*/
private final void step3() {
if (k == 0)
return; /* For Bug 1 */
switch (b[k - 1]) {
case 'a':
if (ends("ational")) {
r("ate");
break;
}
if (ends("tional")) {
r("tion");
break;
}
break;
case 'c':
if (ends("enci")) {
r("ence");
break;
}
if (ends("anci")) {
r("ance");
break;
}
break;
case 'e':
if (ends("izer")) {
r("ize");
break;
}
break;
case 'l':
if (ends("bli")) {
r("ble");
break;
}
if (ends("alli")) {
r("al");
break;
}
if (ends("entli")) {
r("ent");
break;
}
if (ends("eli")) {
r("e");
break;
}
if (ends("ousli")) {
r("ous");
break;
}
break;
case 'o':
if (ends("ization")) {
r("ize");
break;
}
if (ends("ation")) {
r("ate");
break;
}
if (ends("ator")) {
r("ate");
break;
}
break;
case 's':
if (ends("alism")) {
r("al");
break;
}
if (ends("iveness")) {
r("ive");
break;
}
if (ends("fulness")) {
r("ful");
break;
}
if (ends("ousness")) {
r("ous");
break;
}
break;
case 't':
if (ends("aliti")) {
r("al");
break;
}
if (ends("iviti")) {
r("ive");
break;
}
if (ends("biliti")) {
r("ble");
break;
}
break;
case 'g':
if (ends("logi")) {
r("log");
break;
}
}
}
/* step4() deals with -ic-, -full, -ness etc. similar strategy to step3. */
private final void step4() {
switch (b[k]) {
case 'e':
if (ends("icate")) {
r("ic");
break;
}
if (ends("ative")) {
r("");
break;
}
if (ends("alize")) {
r("al");
break;
}
break;
case 'i':
if (ends("iciti")) {
r("ic");
break;
}
break;
case 'l':
if (ends("ical")) {
r("ic");
break;
}
if (ends("ful")) {
r("");
break;
}
break;
case 's':
if (ends("ness")) {
r("");
break;
}
break;
}
}
/* step5() takes off -ant, -ence etc., in context <c>vcvc<v>. */
private final void step5() {
if (k == 0)
return; /* for Bug 1 */
switch (b[k - 1]) {
case 'a':
if (ends("al"))
break;
return;
case 'c':
if (ends("ance"))
break;
if (ends("ence"))
break;
return;
case 'e':
if (ends("er"))
break;
return;
case 'i':
if (ends("ic"))
break;
return;
case 'l':
if (ends("able"))
break;
if (ends("ible"))
break;
return;
case 'n':
if (ends("ant"))
break;
if (ends("ement"))
break;
if (ends("ment"))
break;
/* element etc. not stripped before the m */
if (ends("ent"))
break;
return;
case 'o':
if (ends("ion") && j >= 0 && (b[j] == 's' || b[j] == 't'))
break;
/* j >= 0 fixes Bug 2 */
if (ends("ou"))
break;
return;
/* takes care of -ous */
case 's':
if (ends("ism"))
break;
return;
case 't':
if (ends("ate"))
break;
if (ends("iti"))
break;
return;
case 'u':
if (ends("ous"))
break;
return;
case 'v':
if (ends("ive"))
break;
return;
case 'z':
if (ends("ize"))
break;
return;
default:
return;
}
if (m() > 1)
k = j;
}
/* step6() removes a final -e if m() > 1. */
private final void step6() {
j = k;
if (b[k] == 'e') {
int a = m();
if (a > 1 || a == 1 && !cvc(k - 1))
k--;
}
if (b[k] == 'l' && doublec(k) && m() > 1)
k--;
}
/**
* Stem the word placed into the Stemmer buffer through calls to add().
* Returns true if the stemming process resulted in a word different
* from the input. You can retrieve the result with
* getResultLength()/getResultBuffer() or toString().
*/
public void stem() {
k = i - 1;
if (k > 1) {
step1();
step2();
step3();
step4();
step5();
step6();
}
i_end = k + 1;
i = 0;
}
}
}