title: Error in `[.data.frame`(ozone, , 2) : undefined columns selected
body: <p>I wanted to Represent scatter on a graph by using plot() function and passing it a data which is a file in my local file system, but I'm getting this error, I tried to set names for the header with colnames() function but same error </p>
  
  <pre><code>    ozone &lt;- read.table("C:/Users/Abde/Downloads/donnees_rennes_O3.txt",header=T,sep="\t");
  head(mydata);
  Date......O3......T12......T15......Ne12......N12......S12......E12......W12......Vx......O3v
  1    19960422      63.6      13.4      15      7      0      0      3      0      9.35      95.6
  2    19960429      89.6      15      15.7      4      3      0      0      0      5.4      100.2
  3    19960506      79      7.9      10.1      8      0      0      7      0      19.3      105.6
  4  19960514      81.2      13.1      11.7      7      7      0      0      0      12.6      95.2
  5     19960521      88      14.1      16      6      0      0      0      6      -20.3      82.8
  6 19960528      68.4      16.7      18.1      7      0      3      0      0      -3.69      71.4
  
  plot(O3,T12,data=mydata,xlab="T12",ylab="O3");
  
  &gt;Error in plot(O3, T12, data = ozone, xlab = "T12", ylab = "O3") : 
  object 'O3' not found
  </code></pre>