验证对象在R中的函数中是否存在 [英] Verify object existence inside a function in R

问题描述

我想确定对象是否存在于R中的函数中:

I want to determine whether an object exists inside a function in R:

foo <- function() {
 y <- "hello" 
 if (exists(y, envir = sys.frame())) print(y)
}
foo()

存在错误(y，envir = sys.frame()):第一个参数无效

Error in exists(y, envir = sys.frame()) : invalid first argument

我认为添加envir = sys.frame()可以解决问题.还尝试了envir = environment()

I thought adding the envir = sys.frame() would do the trick. Also tried envir = environment()

期望

foo()
"hello"

推荐答案

您应已选中?exists:

Usage:

     exists(x, where = -1, envir = , frame, mode = "any",
            inherits = TRUE)

Arguments:

       x: a variable name (given as a character string).

执行exists("y")

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