. of  30 variables:</span>
<span class="r-out co"><span class="r-pr">#&gt;</span>  $ year   : int  1964 1964 1964 1964 1964 1964 1964 1964 1964 1964 ...</span>
<span class="r-out co"><span class="r-pr">#&gt;</span>  $ month  : int  1 2 3 4 5 6 7 8 9 10 ...</span>
<span class="r-out co"><span class="r-pr">#&gt;</span>  $ prccem : int  NA NA NA NA NA NA NA NA NA NA ...</span>
<span class="r-out co"><span class="r-pr">#&gt;</span>  $ ipcem  : num  0.474 0.531 0.643 0.826 1.027 ...</span>
<span class="r-out co"