title: Remove periods before the first comma in a string
body: <p>How can I remove the periods before the first comma in these strings?  </p>
  
  <pre><code> xx &lt;- c("fefe.3. fregg, ff, 34.gr. trgw", 
            "fefe3. fregg, ff, 34.gr. trgw",
            "fefe3 fregg, ff, 34.gr. tr.gw")
  </code></pre>
  
  <p>Desired output:</p>
  
  <pre><code>    "fefe3 fregg, ff, 34.gr. trgw"
      "fefe3 fregg, ff, 34.gr. trgw"
      "fefe3 fregg, ff, 34.gr. tr.gw" 
  </code></pre>
  
  <p>I've started with <code>gsub("\\.","", xx))</code>, which removes all periods. How to change it to specify 'only the period before the first comma'?</p>