title: R: numeric vector becoming non-numeric after cbind of dates
body: <p>I have a numeric vector (future_prices) in my case. I use a date vector from another vector (here:  pred_commodity_prices$futuredays) to create numbers for the months. After that I use cbind to bind the months to the numeric vector. However, was happened is that the numeric vector become non-numeric. Do you know how what the reason for this is? When I use as.numeric(future_prices) I get strange values. What could be an alternative? Thanks</p>
  
  <pre><code>head(future_prices)
  pred_peak_month_3a pred_peak_quarter_3a 
  1           68.33907             62.37888
  2           68.08553             62.32658
  
  is.numeric(future_prices)
  [1] TRUE
  &gt; month = format(as.POSIXlt.date(pred_commodity_prices$futuredays), "%m")
  &gt; future_prices &lt;- cbind (future_prices, month)
  &gt; head(future_prices)
    pred_peak_month_3a     pred_peak_quarter_3a   month
    1 "68.3390747063745"   "62.3788824938719"     "01"
   is.numeric(future_prices)
   [1] FALSE 
  </code></pre>