title: How to extract first occurrence of alphabets in a string in R?
body: <p>I have a character column having values like <code>"CHELSEAFC17FEB640CE"</code>, <code>"BARCAFC17FEB1400CE"</code>. I want to extract characters <code>"CHELSEAFC"</code>, <code>"BARCAFC"</code> and so on. Currently I am using 
  <code>regmatches(x$symbol,regexpr("[A-z]+",x$symbol))</code> 
  but getting an error:</p>
  
  <blockquote>
    <p>Error in <code>$&lt;-.data.frame</code>(<code>*tmp*</code>, "cg", value = c("CHELSEAFC",
    "CHELSEAFC", "TOTTENHAMFC",  :    replacement has 11366767 rows, data
    has 11366772 Calls: $&lt;- -> $&lt;-.data.frame Execution halted</p>
  </blockquote>
  
  <p>I can't seem to find the problem row. Please somebody help with debugging or suggest a better way to do this :)</p>