the characters for the corresponding
futures series. Usually in the form of
CHRIS/EXCHANGE_SYMBOL, such as CHRIS/CME_CL for light,
sweet crude oil, and CHRIS/CME_GC for gold.
start_date
a character string date in the form of
yyyy-mm-dd such as 2000-01-01
end_date
a character string date identical to the
above
verbose
an argument that displays how many NA and
spike days were removed, then prints the removed dates