Find Packages that Contain an Object

what	the name of an object, or, if simple.words = TRUE, a regular expression. what can be either a name or a character string; however, a character string is recommended for compatibility.
mode	a character string. If it is not the default ("any"), only objects whose mode is mode are considered.
numeric	a logical value. If numeric = TRUE, it returns the position in search() list. Otherwise, it returns the name of the package.
simple.words	a logical value. If TRUE (the default), the what object names must match what exactly. If FALSE, what is treated as a regular expression.

If numeric = FALSE (the default), returns a character vector of names of packages that contain what.
If numeric = TRUE, returns a numeric vector of positions (in search()) of packages that contain what. The names of the vector contains the corresponding package name.

find("sin") # [1] "package:base"

find("sin", num=TRUE) # package:base # 9

find("some strange name") # character(0)

find("sta", mode = "list", num = TRUE, simple.words = FALSE)

find("stack", mode = "list", num = TRUE, simple.words = TRUE)

find("stack", num = TRUE, simple.words = TRUE)

find("stack", mode = "any", num = TRUE, simple.words = FALSE)

find(".data.frame$", simple.words = FALSE)