A vector of tickers. If not sure whether the ticker is available, check the websites of google and yahoo finance. The source for downloading
the data can either be Google or Yahoo. The function automatically selects the source webpage based on the input ticker.
src
Source of data (yahoo or google)
first.date
The first date to download data (date or char as YYYY-MM-DD)
last.date
The last date to download data (date or char as YYYY-MM-DD)