title: Running StringToWordVector filter in WEKA
body: <p>I am using WEKA's API on Java to develop an application. When running StringToWordVector filter (to convert the string type attributes) to my input.arff file that looks like this:</p>
  
  <pre><code>    @relation Instantzien_Bektorea
  
      @attribute 5_Ainf_Lema string
      @attribute 6_Arg_PosKat {IZE,ADJ,ADI,ADB,DET,IOR,LOT,PRT,ITJ,BST,ADL,ADT,SIG,SNB,LAB,POST}
      @attribute 7_Arg_Pos_AzpiKat {ARR,IZB,LIB,ZKI,GAL,SIN,ADK,ADP,FAK,ERKARR,ERKIND,NOLARR,NOLGAL,DZH,BAN,ORD,DZG,ORO,PERARR,PERIND,IZGMGB,IZGGAL,BIH,ELK,JOK,JNT,HUTSA}
      @attribute 8_Arg_Kasua {abl,abu,abz,ala,soz,dat,des,erg,gel,gen,ine,ins,mot,abs,par,pro,bnk,desk,aurk,bald,emen,erlt,espl,haut,helb,kaus,konpl,kont,denb,mod,mos,ondo,zhg,neg,gen_post_ine,gen_post,gen_post_abs,ala_des,soz_post_ala,zero_post_abl,-}
      @attribute 9_Argumentuaren_FSint {-,subj,obj}
      @attribute 10_Arg_Posizioa {Aurretik,Atzetik}
      @attribute 11_Dist_HKop numeric
      @attribute 12_Dist_ArgKop numeric
      @attribute 13_Framea string
      @attribute 15_Frame_Unekoa string
      @attribute Klasea {arg0,arg1,arg2,argM*LOC,argM*TMP,argM*MNR,argM*Cause,argM*ADV,argM*PRP,argM*-,argM*NEG,argM*DIS}
  
      @data
      eta_gero,LOT,ARR,denb,-,Aurretik,999,1,argM_PRED_arg1,ARGM_PRED_arg1,argM*TMP
      Ainf_Lema,ADI,SIN,mod,-,Aurretik,1,1,argM_arg0_arg1_PRED,argM_arg0_ARG1_PRED,arg1
      Ainf_Lema,IZE,ARR,abs,subj,Aurretik,999,2,arg0_argM_arg1_PRED,ARG0_argM_arg1_PRED,arg0
  ... 
  </code></pre>
  
  <p>I get another a bunch of instances that wrote in output.arrf look like this:</p>
  
  <pre><code>@relation 'Train_Instantzien_Bektorea-weka.filters.unsupervised.attribute.StringToWordVector-R1,9,10-W1000-prune-rate-1.0-N0-stemmerweka.core.stemmers.NullStemmer-M1-tokenizerweka.core.tokenizers.WordTokenizer -delimiters \" \\r\\n\\t.,;:\\\'\\\"()?!\"'
  
  @attribute 6_Arg_PosKat {IZE,ADJ,ADI,ADB,DET,IOR,LOT,PRT,ITJ,BST,ADL,ADT,SIG,SNB,LAB,POST}
  @attribute 7_Arg_Pos_AzpiKat {ARR,IZB,LIB,ZKI,GAL,SIN,ADK,ADP,FAK,ERKARR,ERKIND,NOLARR,NOLGAL,DZH,BAN,ORD,DZG,ORO,PERARR,PERIND,IZGMGB,IZGGAL,BIH,ELK,JOK,JNT,HUTSA}
  @attribute 8_Arg_Kasua {abl,abu,abz,ala,soz,dat,des,erg,gel,gen,ine,ins,mot,abs,par,pro,bnk,desk,aurk,bald,emen,erlt,espl,haut,helb,kaus,konpl,kont,denb,mod,mos,ondo,zhg,neg,gen_post_ine,gen_post,gen_post_abs,ala_des,soz_post_ala,zero_post_abl,-}
  @attribute 9_Argumentuaren_FSint {-,subj,obj}
  @attribute 10_Arg_Posizioa {Aurretik,Atzetik}
  @attribute 11_Dist_HKop numeric
  @attribute 12_Dist_ArgKop numeric
  @attribute Klasea {arg0,arg1,arg2,argM*LOC,argM*TMP,argM*MNR,argM*Cause,argM*ADV,argM*PRP,argM*-,argM*NEG,argM*DIS}
  @attribute ARG0_PRED_arg1 numeric
  @attribute ARG0_arg1_PRED numeric
  @attribute ARG0_arg1_PRED_arg1_argM numeric
  @attribute ARG0_arg1_PRED_argM numeric
  @attribute ARG0_arg1_PRED_argM_argM numeric
  @attribute ARG0_argM_PRED numeric
  
  ...
  
  @attribute argM_PRED_ARG1_argM_argM numeric
  @attribute argM_PRED numeric
  @attribute argM_PRED_arg1_ARGM numeric
  
  ...
  
  @attribute ARGM_argM_PRED_arg1_argM numeric
  @attribute arg0_ARGM_arg1_PRED numeric
  @attribute arg0_ARGM_arg1_PRED_argM numeric
  @attribute arg0_arg1_PRED_ARGM_argM numeric
  @attribute eta_gero numeric
  @attribute gaur numeric
  
  
  @data
  {0 LOT,2 denb,5 999,6 1,7 argM*TMP,90 1,162 1,197 1}
  {0 ADI,1 SIN,2 mod,5 1,6 1,7 arg1,19 1,42 1,93 1}
  {2 abs,3 subj,5 999,6 2,16 1,19 1,29 1} 
  </code></pre>
  
  <p>As you will see in the output.arff file some attributes disappear from the instances (first instance-> no first attribute, no third attribute etc.) Why is this??</p>
  
  <p>The Java code that runs the filter looks like this:</p>
  
  <pre><code>      // StringToWordVector filter
        String[] options = new String[1];
        options[0] = "-R &lt;1,9,10&gt;";                                    
        StringToWordVector filter = new StringToWordVector(); 
        filter.setOptions(options);                          
        filter.setInputFormat(input.arff);                         
        Instances output_inst = Filter.useFilter(input_inst, filter);
  </code></pre>
  
  <p>Any ideas where the problem can be? Thank you very much.</p>