Extraer frases clave del texto (de 1 a 4 palabras)

Question

¿Cuál es la mejor forma de extraer frases clave de un bloque de texto? Estoy escribiendo una herramienta para hacer la extracción de palabras clave: something like this. He encontrado algunas bibliotecas para Python y Perl para extraer n-grams, pero estoy escribiendo esto en Node, así que necesito una solución de JavaScript. Si no hay ninguna biblioteca de JavaScript existente, ¿alguien podría explicar cómo hacer esto para que yo solo pueda escribirlo?

Answer 1

me gusta la idea, así que he implementó: Ver abajo (comentarios descriptivos se incluyen).
Vista previa en: http://fiddle.jshell.net/WsKMx/

/*@author Rob W, created on 16-17 September 2011, on request for Stackoverflow (http://stackoverflow.com/q/7085454/938089) 
* Modified on 17 juli 2012, fixed IE bug by replacing [,] with [null] 
* This script will calculate words. For the simplicity and efficiency, 
* there's only one loop through a block of text. 
* A 100% accuracy requires much more computing power, which is usually unnecessary 
**/ 


var text = "A quick brown fox jumps over the lazy old bartender who said 'Hi!' as a response to the visitor who presumably assaulted the maid's brother, because he didn't pay his debts in time. In time in time does really mean in time. Too late is too early? Nonsense! 'Too late is too early' does not make any sense."; 

var atLeast = 2;  // Show results with at least .. occurrences 
var numWords = 5;  // Show statistics for one to .. words 
var ignoreCase = true; // Case-sensitivity 
var REallowedChars = /[^a-zA-Z'\-]+/g; 
// RE pattern to select valid characters. Invalid characters are replaced with a whitespace 

var i, j, k, textlen, len, s; 
// Prepare key hash 
var keys = [null]; //"keys[0] = null", a word boundary with length zero is empty 
var results = []; 
numWords++; //for human logic, we start counting at 1 instead of 0 
for (i=1; i<=numWords; i++) { 
    keys.push({}); 
} 

// Remove all irrelevant characters 
text = text.replace(REallowedChars, " ").replace(/^\s+/,"").replace(/\s+$/,""); 

// Create a hash 
if (ignoreCase) text = text.toLowerCase(); 
text = text.split(/\s+/); 
for (i=0, textlen=text.length; i<textlen; i++) { 
    s = text[i]; 
    keys[1][s] = (keys[1][s] || 0) + 1; 
    for (j=2; j<=numWords; j++) { 
     if(i+j <= textlen) { 
      s += " " + text[i+j-1]; 
      keys[j][s] = (keys[j][s] || 0) + 1; 
     } else break; 
    } 
} 

// Prepares results for advanced analysis 
for (var k=1; k<=numWords; k++) { 
    results[k] = []; 
    var key = keys[k]; 
    for (var i in key) { 
     if(key[i] >= atLeast) results[k].push({"word":i, "count":key[i]}); 
    } 
} 

// Result parsing 
var outputHTML = []; // Buffer data. This data is used to create a table using `.innerHTML` 

var f_sortAscending = function(x,y) {return y.count - x.count;}; 
for (k=1; k<numWords; k++) { 
    results[k].sort(f_sortAscending);//sorts results 

    // Customize your output. For example: 
    var words = results[k]; 
    if (words.length) outputHTML.push('<td colSpan="3" class="num-words-header">'+k+' word'+(k==1?"":"s")+'</td>'); 
    for (i=0,len=words.length; i<len; i++) { 

     //Characters have been validated. No fear for XSS 
     outputHTML.push("<td>" + words[i].word + "</td><td>" + 
      words[i].count + "</td><td>" + 
      Math.round(words[i].count/textlen*10000)/100 + "%</td>"); 
      // textlen defined at the top 
      // The relative occurence has a precision of 2 digits. 
    } 
} 
outputHTML = '<table id="wordAnalysis"><thead><tr>' + 
       '<td>Phrase</td><td>Count</td><td>Relativity</td></tr>' + 
       '</thead><tbody><tr>' +outputHTML.join("</tr><tr>")+ 
       "</tr></tbody></table>"; 
document.getElementById("RobW-sample").innerHTML = outputHTML; 
/* 
CSS: 
#wordAnalysis td{padding:1px 3px 1px 5px} 
.num-words-header{font-weight:bold;border-top:1px solid #000} 

HTML: 
<div id="#RobW-sample"></div> 
*/ 

Answer 2

No sé tal biblioteca en JavaScript, pero la lógica es texto

1. dividida en una matriz
2. continuación, clasificar y contar

alternativamente

1. dividida en una matriz
2. crear una matriz secundaria
3. que atraviesa cada elemento de la primera matriz
4. comprobación de si existe elemento actual en la matriz secundaria
5. si no existe empuje como clave
6. demás aumentar el valor de un elemento que tiene una clave = al punto buscado. HTH

Ivo Stoykov