> source('letter.frequency.r')
> letter.frequency('letter.frequency.r')
    -  ,  .  '  (  )  [  ]  {  }  <  =  1  a  c  d  e  f  h  i  l  L  m  n  N  o  p  q  r  s  t  u  U  y
22  3  2  1  2  6  6  2  2  1  1  3  1  1  9  6  1 14  7  2  7  8  3  4  6  1  3  3  1  8  8  7  3  1  2