title: { : missing value where TRUE/FALSE needed
body: <p>Here is my code:</p>
  <pre class="lang-r prettyprint-override"><code>tst &lt;- data.frame(ref=c(&quot;A&quot;, &quot;T&quot;, &quot;C&quot;, &quot;C&quot;, &quot;G&quot;, &quot;G&quot;),
                        alt= c(&quot;AAA&quot;, &quot;T&quot;, &quot;A&quot;, &quot;ATCGA&quot;, &quot;G&quot;, &quot;A&quot;))
  for(i in 1:nrow(tst)){
    if(tst[i,2] == &quot;A&quot;){
      tst &lt;- tst[-i,]
    }
  }
  </code></pre>
  <p>but I received this error
  :</p>
  <p><code>Error in if (tst[i, 2] == &quot;A&quot;) { : missing value where TRUE/FALSE needed</code></p>
  <p>Now I don't know how to solve it,
  Thanks for any help</p>