向上移动框架，调试R环境 [英] move up a frame, debug R environment

问题描述

在调试函数时，我想移至父框架并查看那里的一些变量。我该怎么做？

When debugging a function, I would like to move up to the parent frame and look at some variables there. How do I do this?

这里是一个示例：

f <- function() {
   x <-1
   g(x+1)
}
g <- function(z) {
   y = z+2
   return(y)
}

然后我使用<$调试这两个函数c $ c> debug（ g）和 debug（ f）。当我在 Browser> 遇到 g 时，我想返回到 f 检查x。

I then debug both functions using debug("g") and debug("f"). When I end up in g at the Browser>, I would like to move back up to f to examine x.

谢谢

推荐答案

在R术语中，您想调查 g（）的评估环境（即调用 g 的环境）的父框架。 ？sys.parent 的帮助页中记录了执行该操作的功能。

In R terminology, you are wanting to investigate the parent frame of g()'s evaluation environment (i.e. the environment in which g was called). The functions for doing that are documented in the help page for ?sys.parent.

一旦浏览器指示您正在'调试g（x + 1）'，则可以执行以下操作。 （感谢Joshua Ulrich建议使用 where 来帮助定位呼叫堆栈中的位置。）

Once your browser indicates that you are 'debugging in g(x + 1)', you can do the following. (Thanks to Joshua Ulrich for suggesting where to help locate ones position in the call stack .)

# Confirm that you are where you think you are
where
# where 1 at #3: g(x + 1)
# where 2: f()

# Get a reference to g()'s parent frame (an environment object)
pframe <- parent.frame()
pframe
# <environment: 0x019b9174>

# Examine the contents of the parent frame
ls(env=pframe)
# [1] "x"

# Get the value of 'x' in the parent frame
get("x", env = pframe)
# [1] 1

编辑：要了解？sys.parent 中描述的功能集合，可能值得注意的是 parent.frame（）（基本上）是 sys.frame（sys.parent（1））的简写。如果您发现自己位于调用堆栈下方的评估环境中（例如 where 所示），则可以进入备份堆栈更远的环境（例如两个通过 parent.frame（2）或 sys.frame（sys.parent（2））进行下一步）。

EDIT: To understand the collection of functions described in ?sys.parent, it's probably worth noting that parent.frame() is (basically) shorthand for sys.frame(sys.parent(1)). If you find yourself in an evaluation environment farther down a call stack (as revealed by where, for instance), you can reach into environments farther back up the call stack (say two steps up) by either parent.frame(2) or sys.frame(sys.parent(2)).

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