Output set of stock prices from yahoo finance as a matrix with header and dates into excel

Output historical stock prices for a basket of stocks and given period as a matrix with header

This code downloads historical prices for a basket of given stocks ( should be listed in a file S&P.txt ) within a given period and output the prices in a Matrix form with a header of stock symbols and a column of the corresponding dates. It gives the user the option to download daily prices, weekly ( Mon,Tue,.. or Fridays ), or monthly prices.