ustyc - Fetch US Treasury yield curve data.
Forms a query to submit for US Treasury yield curve data,
posting this query to the US Treasury web site's data feed
service. By default the download includes data yield data for
12 products from January 1, 1990, some of which are NA during
this span. The caller can pass parameters to limit the query
to a certain year or year and month, but the full download is
not especially large. The download data from the service is in
XML format. The package's main function transforms that XML
data into a numeric data frame with treasury product items
(constant maturity yields for 12 kinds of bills, notes, and
bonds) as columns and dates as row names. The function returns
a list which includes an item for this data frame as well as
query-related values for reference and the update date from the
service.