c＃中的逆文档频率（IDF）方法出错 [英] error occur in Inverse Document frequency(IDF) method in c#

问题描述

IDF（衡量一个词重要性的流行度量.IDF不可避免地出现在信息检索中使用的一系列启发式测量中。但是，到目前为止，IDF本身就是一种启发式方法。



mathaically IDF是



IDF（t，D）= log（文件总数/文件匹配期限）;

实际上我已经开发了一个用于文档聚类的应用程序。在这里我有



一个IDF方法就像

  private   static   float  FindInverseDocumentFrequency（ string  term）
 {
  / /   DocumentVector dv = new DocumentVector（）;  
 
  //  找到包含谁的术语的文档编号文档集合 
  int  count = documentCollection.ToArray（）。其中​​（s = >  r.Split（s.ToUpper（））。ToArray（）。包含（term.ToUpper（）））。Count（）; 
  / *   
 *集合中文档总数与no之比的日志。包含术语
 *的文档，我们也可以使用Math.Log（count /（1 + documentCollection.Count））来处理除零情况; 
 * /  
  return （ float ）Math.Log（ （ float ）documentCollection.Count /（ float ）count）; 
 
} 
 

此方法在程序中使用以下声明的陈述





documentCollection如

 documentCollection = collection。 DocumentList [dv.content]  as  Hashtable; 
 

DocumentList就像

  private  DocumentCollection docCollection =  new  DocumentCollection（）{DocumentList =  new  Hashtable（）}; 

s就是这样的字符串

 List< string> removeList =  new 列表< string>（）{  \\ \\，  \ rr，  \ n， （， ），   [， ]，  {， }， ，< span class =code-string> 。， ， ，}; 
  foreach （ string  s  in  removeList）
 {
 distinctTerms.Remove（s）; 
} 

r是正则表达式

  private   static 正则表达式r = 新正则表达式（ （[\\t {}（）\，：;。\ n]））; 
 

IDF方法有一些错误如：

 documentcollection.toarray（）发生错误 喜欢 < span class =code-keyword> as  
 
  'System。 Collections.Hashtable'不包含'ToArray'的定义，并且没有扩展方法'ToArray'接受类型'System.Collections.Hashtable'的第一个参数可以找到（你是否缺少using指令或汇编引用？） 

please slove这个错误。





请帮助我。谢谢你

解决方案

不要使用非泛型类型（此处不适用的专用类型除外）。早在.NET v.2.0引入泛型时，它就已经过时了。看看你在做什么：使用的动态案例作为运算符。泛型（+经典OOP）的重点是避免它。



使用类型 System.Collections.Generic.HashSet< T> 而是使用 ToArray< T>（）方法：

https://msdn.microsoft.com/en-us/library/bb359438%28v=vs.110%29。 aspx [ ^ ]，

https ：//msdn.microsoft.com/en-us/library/bb298736（v = vs.110）.aspx [ ^ ]，

https://msdn.microsoft.com/en-us/library/bb298736(v=vs.110).aspx [ ^ ]。

-SA

IDF( is a popular measure of a word's importance. The IDF invari- ably appears in a host of heuristic measures used in information retrieval. However, so far the IDF has itself been a heuristic.

mathamatically IDF is the

IDF(t,D)=log(Total Number documents/Number of Document matching term);
Actually i have develop one application for document clustering. in this i have

one IDF method like as

private static float FindInverseDocumentFrequency(string term)
       {
          // DocumentVector dv = new DocumentVector();

           //find the  no. of document that contains the term in whole document collection
           int count = documentCollection.ToArray().Where(s => r.Split(s.ToUpper()).ToArray().Contains(term.ToUpper())).Count();
           /*
            * log of the ratio of  total no of document in the collection to the no. of document containing the term
            * we can also use Math.Log(count/(1+documentCollection.Count)) to deal with divide by zero case;
            */
           return (float)Math.Log((float)documentCollection.Count / (float)count);

       }

this method use the following declared statments in program


documentCollection like as

documentCollection = collection.DocumentList[dv.content] as Hashtable;

DocumentList is like as

private DocumentCollection docCollection=  new DocumentCollection() { DocumentList = new Hashtable() };

s is the string like as

List<string> removeList = new List<string>(){"\"","\r","\n","(",")","[","]","{","}","","."," ",","};
            foreach (string s in removeList)
            {
                distinctTerms.Remove(s);
            }

r is the Regular expression

private static Regex r = new Regex("([ \\t{}()\",:;. \n])");

IDF method have some error like as:

"

 documentcollection.toarray() occur error like as

"'System.Collections.Hashtable' does not contain a definition for 'ToArray' and no extension method 'ToArray' accepting a first argument of type 'System.Collections.Hashtable' could be found (are you missing a using directive or an assembly reference?)

please slove this error.


please help me.thank u

解决方案

Don't use non-generic types (except specialized which are not applicable here). The have been rendered obsolete as early as of .NET v.2.0 when generics were introduced. Look what you are doing: using dynamic case with as operator. The whole point of generics (+ classic OOP) was to avoid it.

Use the type System.Collections.Generic.HashSet<T> instead, with its ToArray<T>() methods:
https://msdn.microsoft.com/en-us/library/bb359438%28v=vs.110%29.aspx[^],
https://msdn.microsoft.com/en-us/library/bb298736(v=vs.110).aspx[^],
https://msdn.microsoft.com/en-us/library/bb298736(v=vs.110).aspx[^].

—SA

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