title: Error in exprs(eset)
body: <p>I am trying to read probes from a dat file, put them in a vector then put the vector into a subset to be able to concatenate more data to it and write it in a CSV file. Here my piece of code:</p>
  
  <pre><code>library(Biobase)
  library(affy)
  
  affys &lt;- read.csv("address of my dat file")
  affys_vec &lt;- as.vector(affys)[,1]
  
  exprs(eset)[affys_vec,] -&gt; sub.set
  
  write.csv(sub.set,file="subset.csv")
  </code></pre>
  
  <p>However when I reach to the : <code>exprs(eset)[affys_vec,] -&gt; sub.set</code></p>
  
  <p>I get the following error message:</p>
  
  <pre><code>** Error in exprs(eset) :
    error in evaluating the argument object' in selecting a method for function 'exprs':
    Error: object 'eset' not found **
  </code></pre>
  
  <p>Are there any suggestions please?</p>
  
  <p>Thanks,</p>
  
  <p>pqtm</p>