title: Update an entire row in data.table in R
body: <p>I have a data.table object in R that has 9,000 columns.  My code calculates new values for all 9,000 columns at once and returns a vector of values.  I'd like to just replace the row in the data.table with all the values at once.  In a dataFrame object this is easy.  However, I can't figure out how to get that working in a data.table.</p>
  
  <pre><code>d &lt;- data.table(q=c(1,2,3,4,5,6,7,8,9), x=rep(c("a","b","c"),each=3), y=c(1,3,6), v=1:9)
  d[q==1, := c(5,5,5,5)] # FAILS
  d[q==1, ] &lt;- c(5,5,5,5) # FAILS
  </code></pre>
  
  <p>Any idea how to efficiently update the whole row at once?</p>