如何找出正在使用哪个（版本）功能？ [英] How to find out which (version of a) function is being used?

问题描述

问题：

如何确定正在调用哪个版本的函数？例如，如果我在data.frame上使用 unique ，则假定我正在使用 unique.data.frame 。但是，尽管有 raster :: unique ，但没有 unique.raster 函数。但是，如果使用 trace（unique）这样的信息，我只会得到正在使用 unique 函数的信息。

How can I find out which version of a function is being called? For example, if I use unique on a data.frame, I presume that I am using unique.data.frame. However, there is no unique.raster function, although there is a raster::unique. But if I use, e.g., trace(unique), I only get information that the unique function is being used.

例如，我想确认当我呼叫 unique（data.frame（1）），正在调用 unique.data.frame 。

I'd like to confirm, for example, that when I call unique(data.frame(1)), unique.data.frame is being called.

示例：

我很难弄清为什么 unique（raster_object）在命令行而不是在函数内部起作用的原因。显然， unique.default 在函数内部被调用，所以我想明确指出哪个ʻunique。&

I am having trouble figuring out why unique(raster_object) works at the command line but not inside a function. Apparently, unique.default is being called inside the function, so I would like to explicitly state which `unique.&

例如，这有效：

library(raster)
a <- rasterFromXYZ(data.frame(a=1:2,b=2:3,c=3:4))
unique(a)

但是当我将其放入函数中时：

But when I put this in a function:

myfun <- function(){
  a <- rasterFromXYZ(data.frame(a=1:2,b=2:3,c=3:4))
  b <- crop(a, extent(c(1,2,3,4)))
  unique(a)
}

即使软件包使用 raster 作为依赖项，在构建软件包并将其加载到新的R会话中之后，出现错误：

even if the package uses raster as a dependency, after I build the package and load it in a new R session, I get the error:

> myfun()
Error in unique.default(a) : unique() applies only to vectors

即使 sessionInfo（）显示光栅包已加载。

Even though sessionInfo() shows that the raster package is loaded.

并且如果我使用 debug（unique），似乎并没有告诉我正在调用哪个函数：

and if I use debug(unique), it doesn't seem to be telling me which function is being called:

Browse[6]> unique(a)
Error in unique.default(a) : unique() applies only to vectors
Browse[6]> raster::unique(a)
debugging in: raster::unique(a)
debug: standardGeneric("unique")

推荐答案

 myfun <- function(){
   a <- rasterFromXYZ(data.frame(a=1:2,b=2:3,c=3:4))
   b <- crop(a, extent(c(1,2,3,4)))
   raster::unique(a)
 }
 myfun()
#[1] 3 4

如果在S3系统中调度了 unique.raster ，则可以使用 trace（unique），但是由于类 rasterLayer的 unique 方法是S4函数，因此无法使用：

If there were a unique.raster dispatched in the S3 system, you could have used trace(unique), but since the unique method for class "rasterLayer" is an S4 function, that won't work:

> showMethods("unique")
Function: unique (package base)
x="ANY", incomparables="ANY"
x="character", incomparables="missing"
    (inherited from: x="ANY", incomparables="ANY")
x="numeric", incomparables="missing"
    (inherited from: x="ANY", incomparables="ANY")
x="RasterLayer", incomparables="missing"
x="RasterStackBrick", incomparables="missing"

使用其打包位置：

> trace("unique", browser, where=raster)
Tracing function "unique" as seen from package "raster"
[1] "unique"
> myfun()
Tracing unique(xyz[, 1]) on entry 
Called from: eval(expr, envir, enclos)
Browse[1]> 
Browse[1]> c
[1] 3 4
> untrace()
Error in methods::.TraceWithMethods(where = <environment>, untrace = TRUE) : 
  argument "what" is missing, with no default
> untrace("unique",  where=raster)
Untracing function "unique" as seen from package "raster"

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