title: dailyReturn with xts object
body: <p>I am having difficulty using <code>dailyReturn</code> function on an xts object with multiple return series.</p>
  
  <pre><code>a&lt;-Cl(getSymbols("INTC",auto.assign=FALSE))
  b&lt;-Cl(getSymbols("IBM",auto.assign=FALSE))
  a&lt;-merge(a,b)
  dailyReturn(a[,1]) #This works!
  dailyReturn(a) #Only return the result for first series
  apply(a,2, dailyReturn) 
  #Error in array(ans, c(len.a%/%d2, d.ans), if (!all(vapply(dn.ans, is.null,  : 
  length of 'dimnames' [1] not equal to array extent
  </code></pre>
  
  <p>How do I get <code>dailyReturn</code> to return the daily returns for multiple series in xts object?</p>