This section will talk about how we use environments and it's utility functions including <code>environment()</code>, <code>assign()</code>, <code>eval()</code>, <code>get()</code>, etc. Basically, your current working environment is in <code>.GlobalEnv</code>, and each function has it's own environment. <hr> #### Examples: - Environment ``` rm(list = ls()) .GlobalEnv parent.env(a.new.env <- new.env()) parent.env(an.env <- environment()) parent.env(a.base <- baseenv()) parent.env(a.new.env <- new.env(parent = a.base)) ls() ``` At the end, there are 3 environments in the current environment <code>.GlobalEnv</code>. Note that the parent of "a.new.env" is "<environment: base>" rather than "a.base"!! The following example fixes this. - assign(), eval(), and get() ``` rm(list = ls()) .GlobalEnv parent.env(a.parent.env <- new.env()) ### Two of the followings are the same. assign("a.children.env", new.env(), envir = a.parent.env) eval(parse(text = "a.children.env <- new.env()"), envir = a.parent.env) ### Two of the followings are the same. ls() eval(ls(), envir = a.parent.env) ### There is a object inside "a.parent.env". ls(envir = a.parent.env) assign("a.value", 10, envir = a.parent.env) eval(parse(text = "a.value <- a.value + 1"), envir = a.parent.env) ### There are two objects now. ls(envir = a.parent.env) ### This should return 11. get("a.value", envir = a.parent.env) ``` There is a parent environment attached in <code>.GlobalEnv</code>, and a childrend environment attached inside the parent environment. In different environment, the <code>assign()</code> and <code>eval()</code> can alter the objects, and <code>get()</code> can access the object values. - Function is a TEMPORARY environment ``` rm(list = ls()) parent.env(.GlobalEnv) ### This is an interesting result. a.function <- function(){ a <- 1 print(environment()) ### print current environment environment() } an.env <- a.function() ### This is an interesting environment. an.env ### This should be the same as the above. ls(envir = an.env) get("a", envir = an.env) ``` I create an environment where is created by <code>a.function()</code> and executing itself, then I store the environment in </code>.GlobalEnv</code>. --- <div w3-include-html="../preamble_tail_date.html"></div>