title: lme4 error: boundary (singular) fit: see ?isSingular
body: <p>I am trying to run <code>lme4</code> package in R. I have 10 Lines in total with four plants for each line in each of the two replications. But some of the plants died and there are some missing values. <code>Weight</code> is the response variable. Here are some lines from the data:</p>
  <pre><code>Line    Rep Weight  PLANT
  Line 1  1   NA  1
  Line 1  1   NA  2
  Line 1  1   NA  3
  Line 1  1   NA  4
  Line 2  1   26  1
  Line 2  1   26  2
  Line 2  1   26  3
  Line 2  1   27  4
  Line 1  2   26  1
  Line 1  2   28  2
  Line 1  2   26  3
  Line 1  2   25  4
  Line 2  2   24  1
  Line 2  2   26  2
  Line 2  2   25  3
  Line 2  2   NA  4
  </code></pre>
  <p>I want to run linear mixed model using <code>lme4</code> package so I tried running:</p>
  <pre><code>lme4 &lt;- lmer(Weight ~ 1 + (1|Rep:Plant), data=Data)
  </code></pre>
  <p>But I got an error:</p>
  <blockquote>
  <p>boundary (singular) fit: see ?isSingular</p>
  </blockquote>
  <pre><code>&gt; dput(Data)
  structure(list(Line = c(&quot;Line 1&quot;, &quot;Line 1&quot;, &quot;Line 1&quot;, &quot;Line 1&quot;, 
  &quot;Line 2&quot;, &quot;Line 2&quot;, &quot;Line 2&quot;, &quot;Line 2&quot;, &quot;Line 1&quot;, &quot;Line 1&quot;, &quot;Line 1&quot;, 
  &quot;Line 1&quot;, &quot;Line 2&quot;, &quot;Line 2&quot;, &quot;Line 2&quot;, &quot;Line 2&quot;), Rep = c(1, 
  1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2), Weight = c(NA, 
  NA, NA, NA, 26, 26, 26, 27, 26, 28, 26, 25, 24, 26, 25, NA), 
      PLANT = c(1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3, 4)), row.names = c(NA, 
  -16L), class = c(&quot;tbl_df&quot;, &quot;tbl&quot;, &quot;data.frame&quot;))
  </code></pre>
  <p>I am using it for the first time and I am not sure about the error. I will appreciate any help!</p>