title: Writing to txt file creates unwanted first column
body: <p>I have this <code>data frame</code> called "<code>Datos</code>" (summary):</p>
  
  <p><code>Datos[1:10,1:5]</code>:</p>
  
  <pre><code> RUN_ADM                                        NOM_ADM RUN_FM Tipo.de.Fondo.Mutuo FECHA_INF
  1  96767630 BANCHILE ADMINISTRADORA GENERAL DE FONDOS S.A.   8001                   5  19860902
  2  96767630 BANCHILE ADMINISTRADORA GENERAL DE FONDOS S.A.   8001                   5  19860903
  3  96767630 BANCHILE ADMINISTRADORA GENERAL DE FONDOS S.A.   8001                   5  19860904
  4  96767630 BANCHILE ADMINISTRADORA GENERAL DE FONDOS S.A.   8001                   5  19860905
  5  96767630 BANCHILE ADMINISTRADORA GENERAL DE FONDOS S.A.   8001                   5  19860906
  6  96767630 BANCHILE ADMINISTRADORA GENERAL DE FONDOS S.A.   8001                   5  19860907
  7  96767630 BANCHILE ADMINISTRADORA GENERAL DE FONDOS S.A.   8001                   5  19860908
  8  96767630 BANCHILE ADMINISTRADORA GENERAL DE FONDOS S.A.   8001                   5  19860909
  9  96767630 BANCHILE ADMINISTRADORA GENERAL DE FONDOS S.A.   8001                   5  19860910
  10 96767630 BANCHILE ADMINISTRADORA GENERAL DE FONDOS S.A.   8001                   5  19860911
  </code></pre>
  
  <p>Where Datos[1:10,1] (<code>$RUN_ADM</code>):</p>
  
  <pre><code>[1] 96767630 96767630 96767630 96767630 96767630 96767630 96767630 96767630 96767630 96767630
  </code></pre>
  
  <p>Then I <code>subset</code>:</p>
  
  <pre><code>  Datos2&lt;-subset(Datos,Datos[,4]==5)
  </code></pre>
  
  <p>And then write into txt file:</p>
  
  <pre><code>write.table(Datos2,"C:/Users/Tomas/Desktop/Memoria de Titulo/CartolaTipo5.txt", sep="\t",col.names = TRUE)
  </code></pre>
  
  <p>The thing is that this produces a file with a new column ( the first one ) sort of an ID key. And the colnames are displace:</p>
  
  <pre><code>RUN_ADM NOM_ADM RUN_FM  Tipo.de.Fondo.Mutuo FECHA_INF
  1   96767630    BANCHILE ADMINISTRADORA GENERAL DE FONDOS S.A.  8001    5
  2   96767630    BANCHILE ADMINISTRADORA GENERAL DE FONDOS S.A.  8001    5
  3   96767630    BANCHILE ADMINISTRADORA GENERAL DE FONDOS S.A.  8001    5
  4   96767630    BANCHILE ADMINISTRADORA GENERAL DE FONDOS S.A.  8001    5
  5   96767630    BANCHILE ADMINISTRADORA GENERAL DE FONDOS S.A.  8001    5
  6   96767630    BANCHILE ADMINISTRADORA GENERAL DE FONDOS S.A.  8001    5
  7   96767630    BANCHILE ADMINISTRADORA GENERAL DE FONDOS S.A.  8001    5
  8   96767630    BANCHILE ADMINISTRADORA GENERAL DE FONDOS S.A.  8001    5
  9   96767630    BANCHILE ADMINISTRADORA GENERAL DE FONDOS S.A.  8001    5
  10  96767630    BANCHILE ADMINISTRADORA GENERAL DE FONDOS S.A.  8001    5
  </code></pre>
  
  <p>Now my first column "RUN_ADM" is:</p>
  
  <pre><code>RUN_ADM
  1
  2
  3
  4
  5
  6
  7
  8
  9
  10
  </code></pre>
  
  <p>What do I have to do to avoid this first new column ?</p>