estimates: Estimate Helper
In chrishaarstick/madstork.opt: MadStork Portfolio Optimization

Function to create a new estimates object. If prices not supplied, get_prices function called and returns calculated. Alternatively, returns and prices can be supplied.

1 2	estimates(symbols, start_date, end_date, grain, periods = 1, prices = NULL, returns = NULL)

`symbols`	vector of security symbols
`start_date`	start date for historical prices
`end_date`	end date for historical prices
`grain`	time grain of returns. Can be either day, week, month, year
`periods`	number of time periods
`prices`	optional input for security prices
`returns`	optional input for security returns