getSymbols('APPL',src='yahoo')
平时都是可以得到APPL的股票的，但是这次突然返回
Error in download.file(paste(yahoo.URL, "s=", Symbols.name, "&a=", from.m,  :
  cannot open URL 'http://ichart.finance.yahoo.com/table.csv?s=APPL&a=0&b=01&c=2007&d=2&e=12&f=2016&g=d&q=q&y=0&z=APPL&x=.csv'
In addition: Warning message:
In download.file(paste(yahoo.URL, "s=", Symbols.name, "&a=", from.m,  :
  cannot open URL 'http://ichart.finance.yahoo.com/table.csv?s=APPL&a=0&b=01&c=2007&d=2&e=12&f=2016&g=d&q=q&y=0&z=APPL&x=.csv': HTTP status was '404 Not Found'