determines (or estimates) the expiration from an xts object by either
finding the last row that is not NA or by passing the name/symbol
of the xts object to expires.character
# S3 method for xts
expires(x, Date, expired = TRUE, silent = FALSE,
src = c("data", "instrument"), ...)either “data” or “instrument”.
If src is “data”, the returned value will be the
index of the last price that is not NA (price is determined by
quantmod:::getPrice. getPrice arguments symbol and
prefer can be passed through dots.)
If src is “instrument” the symbol of the xts object will
be passed to expires.character