Frequencies for first 10,000 rows of echocard variable in namcs2007 dataset :

echocardiog |
        ram |      Freq.     Percent        Cum.
------------+-----------------------------------
         no |      9,946       99.46       99.46
        yes |         54        0.54      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 28 Mar 2016