title: Summarising giving same value for each group
body: <p>using code to get mean petal length for each specie</p>
  
  <pre><code>group_sp&lt;-group_by(iris,iris$Species)
  mean_plength&lt;-summarise(group_sp,mean(iris$Petal.Length))
  mean_plength
  </code></pre>
  
  <p>getting output </p>
  
  <pre><code>`iris$Species` `mean(iris$Petal.Length)`
            &lt;fctr&gt;                     &lt;dbl&gt;
  1         setosa                     3.758
  2     versicolor                     3.758
  3      virginica                     3.758
  </code></pre>
  
  <p>same for all which is not the case it should be rather</p>
  
  <pre><code>setosa  1.464
  versicolor  4.26
  virginica   5.552
  </code></pre>
  
  <p>this is happening for all of my datasets can anyone tell whats the problem</p>