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183 lines
7.3 KiB
183 lines
7.3 KiB
// Identificator.java
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// -----------------------
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// (C) by Marc Nause; marc.nause@audioattack.de
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// first published on http://www.yacy.net
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// Braunschweig, Germany, 2008
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//
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// $LastChangedDate: 2008-05-23 23:00:00 +0200 (Fr, 23 Mai 2008) $
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// $LastChangedRevision: 4824 $
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// $LastChangedBy: low012 $
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//
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 2 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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//
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// Using this software in any meaning (reading, learning, copying, compiling,
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// running) means that you agree that the Author(s) is (are) not responsible
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// for cost, loss of data or any harm that may be caused directly or indirectly
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// by usage of this softare or this documentation. The usage of this software
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// is on your own risk. The installation and usage (starting/running) of this
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// software may allow other people or application to access your computer and
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// any attached devices and is highly dependent on the configuration of the
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// software which must be done by the user of the software; the author(s) is
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// (are) also not responsible for proper configuration and usage of the
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// software, even if provoked by documentation provided together with
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// the software.
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//
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// Any changes to this file according to the GPL as documented in the file
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// gpl.txt aside this file in the shipment you received can be done to the
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// lines that follows this copyright notice here, but changes must not be
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// done inside the copyright notive above. A re-distribution must contain
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// the intact and unchanged copyright notice.
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// Contributions and changes to the program code must be marked as such.
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package de.anomic.language.identification;
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import java.util.Iterator;
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import java.util.List;
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import java.util.Vector;
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/**
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* This class can try to identify the language a text is written in.
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*/
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public final class Identificator {
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private LanguageStatisticsHolder languages;
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public Identificator() {
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languages = LanguageStatisticsHolder.getInstance();
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}
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/**
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* This method tries to return the language a text is written in. The method will only
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* use the first 100000 characters of the text which should be enough. Using more
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* characters probably only slows down the process without gaining much accuracy.
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* @param text the text that is to be analyzed
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* @return the language or "unknown" if the method was not able to find out the language
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*/
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public String getLanguage(String text) {
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// only test the first 100000 characters of a text
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return getLanguage(text, 100000);
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}
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/**
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* This method tries to return the language a text is written in. The method will
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* use the number characters defined in the parameter limit.
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* @param text the text that is to be analyzed
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* @param limit the number of characters that are supposed to be considered
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* @return the language or "unknown" if the method was not able to find out the language
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*/
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public String getLanguage(String text, int limit) {
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String ret = null;
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LanguageStatistics testStat = new LanguageStatistics("text");
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char[] letter = new char[1];
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float letters = 0;
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int upperLimit = text.length();
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if (upperLimit > limit) {
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upperLimit = limit;
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}
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// count number of characters in text
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for (int i = 0; i < upperLimit; i++) {
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text.getChars(i, i + 1, letter, 0);
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// only count if character is a letter
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if ((letter[0]+"").matches("\\p{L}")) {
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letter[0] = Character.toLowerCase(letter[0]);
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testStat.put(letter[0], testStat.get(letter[0]) + 1);
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letters++;
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}
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}
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// calculate percentage
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Iterator<Character> iter = testStat.keySet().iterator();
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Character character;
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Character maxChar = null;
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float value = 0;
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float max = 0;
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while (iter.hasNext()) {
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character = iter.next();
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value = testStat.get(character);
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if (value > max) {
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maxChar = character;
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max = value;
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}
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testStat.put(character, (value / letters) * 100);
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}
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// create list with relevant languages
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List<Integer> relevantLanguages = new Vector <Integer>();
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for (int i = 0; i < languages.size(); i++) {
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// only languages that contain the most common character in the text will be tested
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if (languages.get(i).contains(maxChar)) {
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relevantLanguages.add(i);
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}
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}
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if (relevantLanguages.size() > 0) {
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// compare characters in text with characters in statistics
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float[] offsetList = new float[relevantLanguages.size()];
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int[] votesList = new int[relevantLanguages.size()];
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iter = testStat.keySet().iterator();
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float minimum;
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float offset = 0;
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float valueCharacter;
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int bestLanguage = -1;
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while (iter.hasNext()) {
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minimum = 100.1f;
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character = iter.next();
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valueCharacter = testStat.get(character);
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for (int i = 0; i < relevantLanguages.size(); i++) {
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value = languages.get(relevantLanguages.get(i)).get(character);
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offset = Math.abs(value - valueCharacter);
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offsetList[i] = offsetList[i] + offset;
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if (offset < minimum) {
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minimum = offset;
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bestLanguage = i;
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}
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}
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votesList[bestLanguage] = ++votesList[bestLanguage];
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}
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// Now we can count how many votes each language got and how far it was away from the stats.
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// If 2 languages have the same amount of votes, the one with the smaller offset wins.
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int maxVotes = 0;
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float minOffset = 100.1f;
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for (int i = 0; i < votesList.length; i++) {
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if ((votesList[i] == maxVotes && offsetList[i] < minOffset) || (votesList[i] > maxVotes)) {
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maxVotes = votesList[i];
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minOffset = offsetList[i];
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bestLanguage = i;
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}
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}
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// Only return name of language of offset is smaller than 20%. This
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// prevents a language beeing reported that has won the voting, but
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// is still not the right language.
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if (offset < 20) {
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ret = languages.get(relevantLanguages.get(bestLanguage)).getName();
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}
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}
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return ret;
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}
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}
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