Function not working withing R function

Question

I'm new to R and was trying to write a function to search for an object in all the environments.

The following piece of lines work fine but when I include them inside a 'while' loop, they don't work. I think I'm missing something here. Any help?

    name<-10
    env=parent.frame()
    !identical(env,emptyenv())
    exists('name',envir=env,inherits = FALSE)
    env<-parent.env(env)
    env

Codes in while loop

    MyWhere<-function(name,env=parent.frame){
       while(!identical(env,emptyenv())){
    if (exists(name,envir=env,inherits = FALSE)) {
        env
       }
    else {
        env<-parent.env(env)
        }
      }
    }

    MyWhere('a')

Error message - Error in exists(name, envir = env, inherits = FALSE) : invalid 'envir' argument

Note that in R, usage of spaces around the <- operator is usually encouraged. — Eike P.
– Eike P., Commented Sep 1, 2015 at 20:37

WhiteViking · Accepted Answer · 2015-09-01 19:28:52Z

1

There's a typo: you need to add parentheses in the call to parent.frame()

MyWhere<-function(name,env=parent.frame()){

Without the parentheses you're passing in a 'function' instead of an 'environment' object, resulting in the error.

answered Sep 1, 2015 at 19:28

WhiteViking

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Comments

josliber · Accepted Answer · 2015-09-01 19:46:24Z

You have a few problems here. The error you're getting is because you're passing parent.env, a function, instead of parent.env(), an environment, as the default environment value.

Further, you don't return the environment when you match the name, which leads to an infinite loop when your function matches. Lastly, the function doesn't return the empty environment when it doesn't match.

When you fix these, it seems to work:

MyWhere<-function(name,env=parent.frame()){
  while(!identical(env,emptyenv())){
    if (exists(name,envir=env,inherits = FALSE)) {
      return(env)
    } else {
      env<-parent.env(env)
    }
  }
  return(env)
}

foo <- 3
MyWhere('foo')
# <environment: R_GlobalEnv>
MyWhere('blah')
# <environment: R_EmptyEnv>
library(ggplot2)
MyWhere('geom_line')
# <environment: package:ggplot2>
# attr(,"name")
# [1] "package:ggplot2"
# attr(,"path")
# [1] "/Library/Frameworks/R.framework/Versions/3.2/Resources/library/ggplot2"

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