Use package API to access object attributes

[Joshua Ulrich]

It is generally a very bad idea to use attr to access (or attr<- to set) attributes of any class you do not own. I noticed at least one place where attr(x, "index") is used instead of index(x) or time(x). This is a very bad practice because it circumvents the zoo and xts APIs.

There is no guarantee that the index of a zoo or xts object must be an attribute and/or named "index". This is true of all the other characteristics of the object classes as well. So you should strongly consider changing all uses of attr to use the provided API functions instead.

[rtsvizteam]

Good point, will fix shortly.

[rtsvizteam]

Code updated