Sometimes it is useful to extract flattened vector of URLs from more complex objects for purposes like subsetting or doing set comparisons.
# S4 method for ShojiCatalog
urls(x)# S4 method for list
urls(x)
# S4 method for character
urls(x)
# S4 method for ShojiOrder
urls(x)
# S4 method for OrderGroup
urls(x)
# S4 method for CrunchVariable
urls(x)
# S4 method for CrunchDataset
urls(x)
A character vector of URLs
a Catalog, Order, or Group object