title: Can't find column that exists in data.table?
body: <p>I am trying to do a group by but says:</p>
  
  <pre><code>library(data.table)
  DT &lt;- fread("C:/Users/user/Desktop/Dataset.csv",encoding = 'UTF-8')
  DT #until this all is fine
  DT[, sum(as.numeric(Ποσότητα), na.rm=TRUE), by=.(user)]
  </code></pre>
  
  <blockquote>
    <p>Error in <code>[.data.table</code>(DT, , sum(as.numeric(Ποσότητα), na.rm = TRUE),
    :    object 'Ποσότητα' not found
    ></p>
  </blockquote>
  
  <pre><code>&gt; colnames(DT)
  
  "Ημερομηνία" "Χρήστης"    "Έργο"       "Εργασία"    "Ποσότητα" 
  
  
  DT$Ποσότητα
    [1] "-"        "-"        "-"        "-"        "222"      "-"        "-"       
    [8] "5"        "1.460,65" "44"
  </code></pre>
  
  <p>its in Greek. Before I translated it but its best to show the actual words.</p>