Abstract:
A method and a storage medium, that includes instructions for causing a computer to implement the method, for document categorization is presented. The method includes identifying terms occurring in a collection of documents, and determining a cohesion score for each of the terms. The cohesion score is a function of a cosine difference between each of the documents containing the term and a centroid of all the documents containing the term. The method further includes sorting the terms based on the cohesion scores. The method also includes creating categories based on the cohesion scores of the terms, wherein each of the categories includes only documents (i) containing a selected one of the terms and (ii) that have not already been assigned to a category. The method still further includes moving each of the documents to a category of a nearest centroid, thereby refining the categories.

Description:
TRADEMARKS 
   IBM® is a registered trademark of International Business Machines Corporation, Armonk, N.Y., U.S.A. Other names used herein may be registered trademarks, trademarks or product names of International Business Machines Corporation or other companies. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to document clustering, and particularly to document clustering based on cohesion terms. 
   2. Description of Background 
   Before our invention, businesses have systematically increased the leverage gained from enterprise data through technologies such as relational database management systems and techniques such as data warehousing. Additionally, it is conjectured that the amount of knowledge encoded in electronic text far surpasses that available in data alone. However, the ability to take advantage of this wealth of knowledge is just beginning to meet the challenge. One important step in achieving this potential has been to structure the inherently unstructured information in meaningful ways. A well-established first step in gaining understanding is to segment examples into meaningful categories. 
   Previous attempts to automatically create categorizations in unstructured data have relied on algorithms created for structured data sets. Such approaches convert text examples into numeric vectors of features, sometimes using latent semantic indexing and principle component analysis to reduce dimensionality, and then cluster the data using well-established clustering techniques such as k-means or Expectation Maximization (EM). These approaches attempt to maximize intra-cluster similarity while minimizing inter-cluster similarity. 
   The problem with approaches of this kind is that they often produce categories that are inexplicable to human interpretation. The fact that a group of documents shares a degree of similarity across an artificial feature space does not insure that the documents in that category taken together construct an easily understood concept. This has led to the problem of cluster naming, to which no practical solution has been found. 
   SUMMARY OF THE INVENTION 
   The shortcomings of the prior art are overcome and additional advantages are provided through the provision of a method (and storage medium that includes instructions for causing a computer to implement the method) for document categorization. The method includes identifying terms occurring in a collection of documents, and determining a cohesion score for each of the terms. The cohesion score is a function of a cosine difference between each of the documents containing the term and a centroid of all the documents containing the term. The method further includes sorting the terms based on the cohesion scores. The method also includes creating categories based on the cohesion scores of the terms, wherein each of the categories includes only documents (i) containing a selected one of the terms and (ii) that have not already been assigned to a category. The method still further includes moving each of the documents to a category of a nearest centroid, thereby refining the categories. 
   System and computer program products corresponding to the above-summarized methods are also described and claimed herein. 
   Additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention. For a better understanding of the invention with advantages and features, refer to the description and to the drawings. 
   As a result of the summarized invention, technically we have achieved a solution where the creation of taxonomies from cohesion terms is easier for a user to interpret than standard statistical approaches. By creating categories that can be described succinctly with a single word or phrase, the prior cluster-naming problem that plagues most other approaches is avoided. This provides an important practical method for quickly understanding the content of a large number of short text documents in any domain. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
       FIG. 1  illustrates one example of a flow chart for a cohesion term taxonomy; 
       FIG. 2  illustrates one example of a flow chart for creation of the categories iteratively; and 
       FIG. 3  illustrates one example of a user interface for the cohesion term taxonomy. 
   

   The detailed description explains the preferred embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
   DETAILED DESCRIPTION OF THE INVENTION 
   Turning now to the drawings in greater detail, it will be seen that in  FIG. 1  there is flow chart illustrating a cohesion term taxonomy, which is applicable to any situation where it is desirable to create a taxonomy across a set of distinct documents. At a block  10 , a minimum category size (M), an uncategorized document size (U), and maximum number of categories (C) is given. At a block  12 , a dictionary (D) of frequently used words/phrases (terms) in a text data set (T) is identified. At a block  14 , the occurrences of dictionary terms in documents of data set T are counted. At a block  16 , the cohesion of each term is a score, which is determined from the sum of the absolute cosine difference between each document containing the term and the centroid of all documents containing the term. At a block  18 , the cohesion scores are normalized by taking into account the size of each term document set. At a block  20 , terms are sorted in order of decreasing cohesion score. At a block  22 , categories are created iteratively. At a block  24 , the resulting categorizations are refined by running one iteration of a k-means algorithm on the set of categories created at block  22 . (i.e., a centroid is created for each category and each document is moved to the category of the closest centroid). 
   The k-means algorithm is a well known algorithm that clusters objects based on attributes into k partitions. It is a variation of the expectation-maximization algorithm that seeks to determine the k means of data generated from Gaussian distributions. It assumes that the object attributes form a vector space. It also seeks to achieve is to minimize total intra-cluster variance, or, the function: 
   
     
       
         
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   where there are k clusters S i , i=1, 2, . . . , k and μ i  is the centroid or mean point of all the points x j εS i . The algorithm starts by partitioning the input points into k initial sets, and then calculates the mean point, or centroid, of each set. It constructs a new partition by associating each point with the closest centroid. Then the centroids are recalculated for the new clusters, and algorithm repeated by alternate application of these two steps until convergence. 
   Turning also to  FIG. 2 , the creation of the categories iteratively is illustrated by a flow chart. At a block  26 , the most cohesion term in the list not yet used is selected. At a block  28 , if the number of uncategorized documents that contain the selected term is greater than the minimum category size, M, then create a category, at a block  29 , consisting of all documents that contain this term still uncategorized. Otherwise stop at a block  31 . At a block  30 , if the number of uncategorized documents remaining is less than U, then STOP (block  31 ). At a block  32 , if the number of categories created is greater than C, then stop (block  31 ). Repeat these steps until a stop criterion is met or no more dictionary terms remain. 
   The dictionary, D is identified at block  12  by representing each document as a vector of weighted frequencies of the document features (i.e., words and phrases), and then using a term-weighting scheme. This scheme emphasizes words with high frequency in a document, and normalizes each document vector to have unit Euclidean norm. For example, if a document were the sentence, “We have no bananas, we have no bananas today,” and the dictionary consisted of only two terms, “bananas” and “today”, then the unnormalized document vector would be {2 1} (i.e., to indicate two bananas and one today), and the normalized version would be: [2/√{square root over (5)}, 1/√{square root over (5)}]. 
   The words and phrases that make up the document feature space are determined by first counting which words occur most frequently (i.e., in the most documents) in the text. A standard “stop word” list is used to eliminate words such as “and”, “but”, and “the”. The top N words are retained in the first pass, where the value of N may vary depending on the length of the documents, the number of documents and the number of categories to be created. Typically N=2000 is sufficient for 10000 short documents of around 200 words to be divided into 30 categories. After selecting the words in the first pass, a second pass is made to count the frequency of the phrases that occur using these words. A phrase is considered to be a sequence of two words occurring in order with out intervening non-stop words. This is repeated so as to keep only the N most frequent words and phrases. This becomes the feature space. A third pass through the data indexes the documents by their feature occurrences. The user may edit this feature space as desired to improve clustering performance. This includes adding in particular words and phrases the user deems to be important, such as named entities like “International Business Machines”. Stemming is usually also incorporated to create a default synonym table that the user may also edit. 
   The occurrences of dictionary terms are counted at block  14  by creating a Sparse Matrix of word occurrences in documents after the third pass through. This matrix records how often each dictionary term occurs in each document. 
   The cohesion of each term are defined at block  16  by defining the cosine distance between any two document vectors (i.e., the cosine distance metric) as: 
   
     
       
         
           
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   The set of documents that match a given term can be represented by a centroid (i.e., average) vector, of all such documents. If the set of documents that match a given term (i.e., the matching set) is defined is represented by, T, then the cohesion of this set is defined to be: 
   
     
       
         
           
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   where T is a text data set containing the documents and n is a normalization parameter. 
   The cohesion scores are normalized at block  18  by taking into account the size of each term document set. The normalization parameter allows the user to compare terms that have different amounts of data. Typically small matching set terms would have an advantage if the normalization parameter, n, were set to 1.0. To adjust for this fact the value of n can be adjusted downward to allow larger matching set terms to be ranked higher if desired. A typical value of n=0.9 is one that seems to work well in many application areas. 
   The dictionary terms are sorted at block  20  in order of decreasing matching set cohesion. Some terms may be eliminated from this list if the matching set size is deemed to small to get an accurate measure of cohesion. 
   Categories are created iteratively at block  22 . Starting with the first term in cohesion order, create mutually exclusive (single membership) categories. The first category contains all documents that contain the most cohesion term. The second category contains all documents that do not contain the most cohesion term, but do contain the second most cohesion term. The third category contains all documents not in the first two categories that contain the third most cohesion term. This category creation method continues until one of the following stopping criteria is met:
         1. The number of uncategorized documents is less than the minimum threshold, U.   2. The number of categories is greater than the maximum threshold, C.   3. No more dictionary terms remain to create categories with.
 
A lower bound is set on the smallest size of an acceptable category. Thus any term that would create a category of size smaller than this threshold (because most of its documents are already contained in previous categories) is skipped.
       

   The resulting categorizations are refined at block  24  by creating a centroid for each category (i.e., an average document vector of all documents contained in the category). Each document is then moved into the category of the centroid it is “nearest” to, using the cosine distance metric. This membership “adjustment” tends to place those documents that could belong to more than one category in the category that is most representative of their overall content. The purpose of this refinement is to properly position those documents that contain more than one of the cohesion terms used in the category creation phase. 
   It will be appreciated that some of the cohesion terms may be excluded from consideration as category definitions, because they do not lead to useful categories. The level of granularity may be set (i.e., the number of categories) by adjusting the threshold U (i.e., the number of uncategorized documents) or n (i.e., the normalization for size). Further, an alternative to normalizing for category size is to specify a minimum category size and then sample all categories to that size when calculating both the centroid and the cohesion values. 
   The k-means clustering described above may create categories that are difficult to interpret by a human being. Typically, cluster-naming approaches attempt to address this issue by adding more and more terms to a name to capture the complex concept that is being modeled by a centroid. Unfortunately, this approach puts the onus on the human interpreter to make sense of what the list of words means and how it relates to the entire set of examples contained in the category. In the present exemplary embodiment, a categorization that is easier to comprehend is to be used. This alternative of putting such documents in more than one category (i.e., multiple membership) is less desirable because it increases the average size of each category and defeats the purpose of summarization via the divide and conquer strategy inherent in a document clustering. Creating multiple copies of documents that match more than one category would be multiplying instead of dividing. Once the clusters are created, they are named with the single term that was used to create each cluster in the first place, thus avoiding the complex name problem associated with k-means clusters. This does not eliminate the need for taxonomy visualization and editing by an analyst, it does however make the process much less cumbersome by creating categories that are (for the most part) fairly easy to comprehend immediately. This is believed to cut the time required to edit each taxonomy by about half (i.e., from around 30 minutes to around 15 minutes per forum). 
   An example shows a set of categories created from documents that are computer help desk problem tickets. The initial categorization created by our approach is illustrated in Table 1 below. 
                                                     TABLE 1                       Class Name   Class Size   Percentage                                        print   824   12.33%           Miscellaneous   689   10.31%           install   394   5.89%           quick_fix   376   5.63%           print_install   289   4.32%           note   254   3.80%           file   221   3.31%           lotus_note   180   2.69%           email   153   2.29%           customer_install   122   1.83%           afs   118   1.77%           address_book   117   1.75%           adsm   110   1.65%           note_email   107   1.60%           network   103   1.54%           print_unable   102   1.53%           password   101   1.51%           database   96   1.44%           email_database   95   1.42%           afs_password   92   1.38%           connect_network   88   1.32%           note_id   88   1.32%           drive   82   1.23%           server_connection   78   1.17%           afs_quota   74   1.11%           install_configure   72   1.08%           reboot_system   70   1.05%           calendar   68   1.02%           personal_address   64   0.96%           ip_address   63   0.94%           netscape   63   0.94%           data_directory   62   0.93%           calendar_profile   61   0.91%           forward_email   60   0.90%           location_document   59   0.88%           configure   56   0.84%           email_template   54   0.81%           email_server   54   0.81%           send_email   53   0.79%           reset   52   0.78%           card   50   0.75%           command_line   44   0.66%           reset_afs   41   0.61%           home_page   41   0.61%           hard   40   0.60%           id   38   0.57%           afs_userid   38   0.57%           softdist   35   0.52%           internet_email   34   0.51%           proxy   33   0.49%           vm_session   32   0.48%           driver   32   0.48%           ring   30   0.45%           file_system   30   0.45%           netdoor   28   0.42%           template   27   0.40%           lan   27   0.40%           monitor   27   0.40%           admin   25   0.37%           copy_file   24   0.36%           socks   24   0.36%           swap   23   0.34%           mouse   19   0.28%           www   19   0.28%           think_pad   18   0.27%           modem   18   0.27%           apps   15   0.22%           serial_number   8   0.12%           Total   6684.0   100.00%                        
The “Miscellaneous” category includes all of the uncategorized documents from the algorithm. These are those documents that did not match any of the cohesion terms before the stopping criteria were met.
 
   In the next step the user selects any categories that are not suitable and also requests that fewer overall categories be created. Turning to  FIG. 3 , the user interface for this interaction is illustrated. 
   The selected terms are removed from consideration as possible cohesion terms. Further the n parameter is decreased from the default of “0.9” to a lower “0.85” thus giving a greater advantage in the selection process to more frequent terms. The result of applying these changes and rerunning the algorithm is illustrated in Table 2 below. 
                                                     TABLE 2                       Class Name   Class Size   Percentage                                        Miscellaneous   1027   15.37%           print   862   12.90%           install   449   6.72%           quick_fix   414   6.19%           email   389   5.82%           print_install   295   4.41%           file   270   4.04%           server   225   3.37%           lotus   216   3.23%           address_book   190   2.84%           afs_password   127   1.90%           customer_install   121   1.81%           id   114   1.71%           email_database   112   1.68%           network   111   1.66%           password   107   1.60%           afs   104   1.56%           database   99   1.48%           adsm   95   1.42%           connect_network   90   1.35%           data_directory   81   1.21%           quota_increase   75   1.12%           hard_drive   74   1.11%           server_connection   73   1.09%           install_configure   69   1.03%           calendar   69   1.03%           configure   63   0.94%           calendar_profile   60   0.90%           ip_address   60   0.90%           email_template   58   0.87%           location_document   54   0.81%           reset   53   0.79%           file_open   50   0.75%           afs_account   42   0.63%           template   39   0.58%           driver   38   0.57%           vm_session   35   0.52%           dialer   34   0.51%           common   33   0.49%           network_connection   32   0.48%           softdist   32   0.48%           ring   28   0.42%           tcp_ip   27   0.40%           respond   24   0.36%           certificate   23   0.34%           home_page   23   0.34%           request_afs   18   0.27%           Total   6684.0   100.00%                        
The user&#39;s request for “fewer classes” requires an adjustment to the allowable size of the uncategorized documents (i.e., the Miscellaneous category) to increase from 10% to 15%. This adjustment in conjunction with the smaller n parameter tends to create a higher level (i.e., more general) set of categories that are more in line with what the user desires. Another iteration, decreasing the normalization parameter to 0.8 and allowing the size of the miscellaneous class to grow to 20% creates the taxonomy shown in Table 3 below.
 
                                                     TABLE 3                       Class Name   Class Size   Percentage                                        Miscellaneous   1395   20.87%           print   890   13.32%           email   568   8.50%           note   481   7.20%           install   479   7.17%           quick_fix   452   6.76%           print_install   298   4.46%           server   283   4.23%           lotus_note   269   4.02%           address_book   181   2.71%           afs   163   2.44%           password   150   2.24%           password_reset   148   2.21%           connect_network   127   1.90%           database   115   1.72%           customer_install   100   1.50%           address   91   1.36%           configure   80   1.20%           adsm   78   1.17%           quota_increase   75   1.12%           install_configure   73   1.09%           reset   64   0.96%           request_customer   58   0.87%           vos   39   0.58%           register_adsm   27   0.40%           Total   6684.0   100.00%                        
After each iteration of the algorithm the categories become somewhat more general, while still retaining much the same flavor.
 
   Implementation as a computer program, written in the Java programming language and executed with the Java virtual machine is illustrated in the Example below, and includes actual Java code along with explanatory annotations. 
   EXAMPLE 
   
     
       
             
           
         
             
                 
             
           
           
             
               public class IntuitiveClustering extends TextClustering implements ActionListener { 
             
             
                float wcohesion[ ] = null; 
             
             
                String tempName = null; 
             
             
                public float granularity = 0.9F; 
             
             
                public HashSet badTerms = new HashSet( ); 
             
             
                TextClustering tc = null; 
             
             
                public transient JDialog jd = null; 
             
             
                transient JRadioButton more = new JRadioButton(Translate.simpleText(“More 
             
             
               Classes”)); 
             
             
                transient JRadioButton less = new JRadioButton(Translate.simpleText(“Fewer 
             
             
               Classes”)); 
             
             
                transient JRadioButton same = new JRadioButton(Translate.simpleText(“Same”),true); 
             
             
                transient JList values = null; 
             
             
                transient JButton Done,Cancel; 
             
             
                public boolean ok = true; 
             
             
                public IntuitiveClustering(TextClustering t) { 
             
             
                 super( ); 
             
             
                 tc = t; 
             
             
                 if (!Util.getParameter(“granularity”).equals(“”)) 
             
             
                  granularity = Util.atof(Util.getParameter(“granularity”)); 
             
             
                } 
             
             
                public void update(float g, String a[ ]) { 
             
             
                 for (int i=0; i&lt;a.length; i++) badTerms.add(a[i]); 
             
             
                 granularity = g; 
             
             
                 wcohesion = null; 
             
             
                 run( ); 
             
             
                } 
             
             
                public void promptForUpdate(Frame f, String title) { 
             
             
                 jd = new JDialog(f,true); 
             
             
                 JPanel buttons = new JPanel( ); 
             
             
                 buttons.setLayout(new FlowLayout( )); 
             
             
                 if (clusterNames==null) clusterNames = tc.clusterNames; 
             
             
                 values = new com.ibm.nls.JList(clusterNames); 
             
             
                 JScrollPane jp = new JScrollPane(values); 
             
             
                 jp.setPreferredSize(new Dimension(500,400)); 
             
             
                 Done = new JButton(“OK”); 
             
             
                 Cancel = new JButton(“Cancel”); 
             
             
                 Done.addActionListener(this); 
             
             
                 Cancel.addActionListener(this); 
             
             
                 buttons.add(Done); 
             
             
                 buttons.add(Cancel); 
             
             
                 ButtonGroup bg = new ButtonGroup( ); 
             
             
                 bg.add(more); 
             
             
                 bg.add(less); 
             
             
                 bg.add(same); 
             
             
                 FlowLayout fl = new FlowLayout( ); 
             
             
                 fl.setHgap(15); 
             
             
                 JPanel jp2 = new JPanel(fl); 
             
             
                 jp2.add(more); 
             
             
                 jp2.add(less); 
             
             
                 jp2.add(same); 
             
             
                 jd.setTitle(title); 
             
             
                 jd.getContentPane( ).setLayout(new BorderLayout(10,10)); 
             
             
                 jd.getContentPane( ).add(“North”,jp); 
             
             
                 jd.getContentPane( ).add(“Center”,jp2); 
             
             
                 jd.getContentPane( ).add(“South”,buttons); 
             
             
                 jd.pack( ); 
             
             
                 jd.show( ); 
             
             
               } 
             
             
               public void actionPerformed(ActionEvent evt) { 
             
             
                if (Done==evt.getSource( )) { 
             
             
                 if (more.isSelected( )) granularity = granularity + 0.05F; 
             
             
                 if (less.isSelected( )) granularity = granularity − 0.05F; 
             
             
                 int v[ ] = values.getSelectedIndices( ); 
             
             
                 for (int i=0; i&lt;v.length; i++) { 
             
             
                  badTerms.add(clusterNames[v[i]]); 
             
             
                  if (Util.getParameter(“append”).equals(“yes”)) { 
             
             
                   try { 
             
             
                    PrintWriter pw = Util.openAppendFile(“stop Words.txt”); 
             
             
                    pw.println(clusterNames[v[i]]); 
             
             
                    pw.close( ); 
             
             
                   } catch (Exception e) {}; 
             
             
                  } 
             
             
                 } 
             
             
                 ok = true; 
             
             
                 jd.dispose( ); 
             
             
                } 
             
             
                if (Cancel==evt.getSource( )) { 
             
             
                 ok = false; 
             
             
                 jd.dispose( ); 
             
             
                } 
             
             
               } 
             
             
               public void run( ) { 
             
             
                System.out.println(“granularity = ” + granularity); 
             
             
                 float ff[ ] = ClusterView.getDataMeans(tc); 
             
             
                 float f[ ] = wordCohesion(tc,ff); 
             
             
                 int order[ ] = Index.run(f); 
             
             
                 int membership[ ] = new int[tc.ndata]; 
             
             
                 for (int i=0; i&lt;tc.ndata; i++) membership[i] = −1; 
             
             
                 order = Util.reverse(order); 
             
             
                 StringVector sv = new StringVector( ); 
             
             
                 HashSet h = new HashSet( ); 
             
             
                 for (int i=0; i&lt;order.length; i++) { 
             
             
                  if (badTerms.contains(tc.attribNames[order[i]])) { 
             
             
                   System.out.println(“bad term: ” + tc attribNames[order[i]]); 
             
             
                   continue; 
             
             
                  } 
             
             
                  StringVector subterms = new StringVector(tc.attribNames[order[i]],“_”); 
             
             
                  if (badTerms.contains(subterms.myElementAt(0))) continue; 
             
             
                  if (subterms.size( )&gt;1 &amp;&amp;badTerms.contains(subterms.myElementAt(1))) 
             
             
               continue; 
             
             
                  float matches = 0.0F; 
             
             
                  if (f[order[i]]==0) break; 
             
             
                  MyIntVector docs = getMatches(order[i], tc); 
             
             
                  for (int j=0; j&lt;docs.size( ); j++) 
             
             
                   if (h.contains(docs.elementAt(j))) 
             
             
                    matches++; 
             
             
                  if (matches/docs.size( )&gt;=0.9F) ; 
             
             
                   // System.out.println(“eliminating ” + tc.attribNames[order[i]] + “ as a 
             
             
               duplicate”); 
             
             
                  else { 
             
             
                   int count = 0; 
             
             
                   for (int j=0; j&lt;docs.size( ); j++) 
             
             
                    if (!h.contains(docs.elementAt(j))) 
             
             
                     count++; 
             
             
                   if ((tc.ndata−h.size( ))/100.0&gt;count) continue; //min size of class is 1% of 
             
             
               remaining data 
             
             
                   if (count&lt;3) continue; 
             
             
                   for (int j=0; j&lt;docs.size( ); j++) { 
             
             
                    if (!h.contains(docs.elementAt(j))) { 
             
             
                     h.add(docs.elementAt(j)); 
             
             
                     membership[docs.myElementAt(j)] = sv.size( ); 
             
             
                    } 
             
             
                   } 
             
             
                   sv.addElement(tc.attribNames[order[i]]); 
             
             
                  } 
             
             
                  //System.out.println(“h.size( ) = ” + h.size( )); 
             
             
                  if (h.size( )&gt;tc.ndata*Math.min(granularity,0.95)) { 
             
             
                   System.out.println(“breaking because granularity = ” + granularity); 
             
             
                   break; 
             
             
                  } 
             
             
                  if (sv.size( )==200) break; 
             
             
                 } 
             
             
                 for (int i=0; i&lt;tc.ndata; i++) 
             
             
                  if (membership[i]==−1) membership[i] = sv.size( ); 
             
             
                 sv.addElement(“Miscellaneous”); 
             
             
                 clusterNames = sv.getStringArray( ); 
             
             
                 nclusters = clusterNames.length; 
             
             
                 input_length = tc.input_length; 
             
             
                 ndata = tc.ndata; 
             
             
                 example = tc.example; 
             
             
                 attribNames = tc.attribNames; 
             
             
                 pointNumber = tc.pointNumber; 
             
             
                 computeMembership(membership); 
             
             
                 classify( ); 
             
             
                 //mergePhraseSimilar( ); 
             
             
                 //classify( ); 
             
             
                 //refine clustering with one step of KMeans 
             
             
                 moveToNearestCentroid( ); 
             
             
                } 
             
             
                public void moveToNearestCentroid( ) { 
             
             
                 TextClustering tc = this; 
             
             
                 float ss[ ] = new float[tc.nclusters]; 
             
             
                 for (int i=0; i&lt;ss.length; i++) 
             
             
                  ss[i] = (float)Math.sqrt(Util.dotProduct(tc.centroids[i],tc.centroids[i])); 
             
             
                 short nextMembership[ ] = new short[tc.ndata]; 
             
             
                 for (int i=0; i&lt;tc.ndata; i++) { 
             
             
                  SmallMatrixRow smr = ClusterManipulation.getSmallRow(tc.example,i); 
             
             
                  int c = AccuracyMetric.getNearestCluster(tc,smr,ss); 
             
             
                  if (tc.clusterNames[tc.smembership[i]].equals(EAdvisor.miscClassName)) 
             
             
                   nextMembership[i] = tc.smembership[i]; 
             
             
                  else 
             
             
                   nextMembership[i] = (short)c; 
             
             
                 } 
             
             
                 tc.computeMembership(nextMembership); 
             
             
                 tc.classify( ); 
             
             
                } 
             
             
               public float[ ] wordCohesion(TextClustering tc, float overallRelev[ ]) { 
             
             
                 float result[ ] = new float[tc.attribNames.length]; 
             
             
                 for (int i=0; i&lt;result.length; i++) { 
             
             
                   MyIntVector docs = getMatches(i, tc); 
             
             
                   result[i] = getAvgDistance(tc,docs.makeArray( )); 
             
             
                     } 
             
             
                 wcohesion = result; 
             
             
                 return(result); 
             
             
                } 
             
             
                public MyIntVector getMatches(int a, TextClustering k) { 
             
             
                 MyIntVector result = new MyIntVector( ); 
             
             
                 SmallSparseMatrix ssm = (SmallSparseMatrix)k.example; 
             
             
                 for (int i=0; i&lt;k.ndata; i++) { 
             
             
                  SmallMatrixRow smr = ssm.getSmallRow(i); 
             
             
                  for (int j=0; j&lt;smr.positions.length; j++) { 
             
             
                   if (smr.positions[j]==a) { 
             
             
                    result.addElement(i); 
             
             
                    break; 
             
             
                   } 
             
             
                  } 
             
             
                 } 
             
             
                 return(result); 
             
             
                } 
             
             
                public float getAvgDistance(KMeans tc, int textDocuments[ ]) { 
             
             
                 if (textDocuments.length==0) return(0.0F); 
             
             
                 float result = 0.0F; 
             
             
                 float centroid[ ] = Util.emptyFloat(tc.input_length); 
             
             
                 for (int i=0; i&lt;textDocuments.length; i++) { 
             
             
                  SmallMatrixRow smr = 
             
             
               ClusterManipulation.getSmallRow(tc.example,textDocuments[i]); 
             
             
                  for (int j=0; j&lt;smr.positions.length; j++) { 
             
             
                   if (smr.positions[j] &gt; −1) { 
             
             
                    centroid[smr.positions[j]]+= smr.multiplier; 
             
             
                   } 
             
             
                  } 
             
             
                 } 
             
             
                 float ss = (float)Math.sqrt(Util.dotProduct(centroid,centroid)); 
             
             
                 for (int i=0; i&lt;textDocuments.length; i++) 
             
             
                 result+= 
             
             
                Math.abs(SmallSparseMatrix.cosDistance(ClusterManipulation.getSmallRow(tc.example, 
             
             
                textDocuments[i]), centroid, ss)); 
             
             
                 float size = (float)Math.pow(textDocuments.length,granularity); 
             
             
                 return(result/size); 
             
             
                } 
             
             
                 
             
           
        
       
     
   
   The capabilities of the present invention can be implemented in software, firmware, hardware or some combination thereof. 
   As one example, one or more aspects of the present invention can be included in an article of manufacture (e.g., one or more computer program products) having, for instance, computer usable media. The media has embodied therein, for instance, computer readable program code means for providing and facilitating the capabilities of the present invention. The article of manufacture can be included as a part of a computer system or sold separately. 
   Additionally, at least one program storage device readable by a machine, tangibly embodying at least one program of instructions executable by the machine to perform the capabilities of the present invention can be provided. 
   The flow diagrams depicted herein are just examples. There may be many variations to these diagrams or the steps (or operations) described therein without departing from the spirit of the invention. For instance, the steps may be performed in a differing order, or steps may be added, deleted or modified. All of these variations are considered a part of the claimed invention. 
   While the preferred embodiment to the invention has been described, it will be understood that those skilled in the art, both now and in the future, may make various improvements and enhancements which fall within the scope of the claims which follow. These claims should be construed to maintain the proper protection for the invention first described.