title: Naming resulting data.table columns after aggregation in R
body: <p>I want to make aggregations in a data.table using functions that return can multiple rows, like <code>summary()</code> or <code>quantile()</code>. The way I do it so far is this:</p>
  
  <pre><code>library(data.table)
  x = as.data.table(iris)
  x[, as.list(c(summary(Sepal.Length), summary(Sepal.Width))), by = Species]
  </code></pre>
  
  <p>This works, but results in arbitrary column names. If I have a vector of length 12, <code>myColumnNames</code>, how can I set the new columns to be named after this vector (without using setnames in the next row)?</p>
  
  <p>My "obvious" attempt, <code>x[, myColumnNames = as.list(c(summary(Sepal.Length), summary(Sepal.Width))), by = Species]</code> failed. Any ideas?</p>