如何重新排序搜索路径？答案

【问题标题】：how to reorder the search path?如何重新排序搜索路径？
【发布时间】：2019-03-24 08:46:38
【问题描述】：

我想将环境（包或其他）附加到位置 2，并且我希望它留在那里。

我可以在大多数情况下使用library 和pos=3 来确保这一点，但我对tidyverse 有疑问：

search()
# [1] ".GlobalEnv"        "tools:rstudio"     "package:stats"    
# [4] "package:graphics"  "package:grDevices" "package:utils"    
# [7] "package:datasets"  "package:methods"   "Autoloads"        
# [10] "package:base" 

something <- list()
attach(something)
library(tidyverse,pos = 3)
search()
# [1] ".GlobalEnv"        "package:forcats"   "package:stringr"  
# [4] "package:dplyr"     "package:purrr"     "package:readr"    
# [7] "package:tidyr"     "package:tibble"    "package:ggplot2"  
# [10] "something"         "package:tidyverse" "tools:rstudio"    
# [13] "package:stats"     "package:graphics"  "package:grDevices"
# [16] "package:utils"     "package:datasets"  "package:methods"  
# [19] "Autoloads"         "package:base"

tidyverse 将其子包附加到pos = 2，我想要一个search 路径以：

search()
# [1] ".GlobalEnv" "something" "package:forcats"...

我怎样才能做到这一点？

【问题讨论】：

标签： r tidyverse r-environment

【解决方案1】：

我可以通过定义 2 个自定义函数来解决它，move_pkg_env 移动 package:* 环境，move_env（使用 move_pkg_env）移动搜索路径中的任何环境，只要只有 package:* 环境在它的位置和目的地之间：

这里是如何使用它：

something <- list()
attach(something)
library(tidyverse,pos = 3)

search()
# [1] ".GlobalEnv"        "package:forcats"   "package:stringr"  
# [4] "package:dplyr"     "package:purrr"     "package:readr"    
# [7] "package:tidyr"     "package:tibble"    "package:ggplot2"  
# [10] "something"         "package:tidyverse" "tools:rstudio"    
# [13] "package:stats"     "package:graphics"  "package:grDevices"
# [16] "package:utils"     "package:datasets"  "package:methods"  
# [19] "Autoloads"         "package:base"

move_env("something", 2)

search()
# [1] ".GlobalEnv"        "something"         "package:forcats"  
# [4] "package:stringr"   "package:dplyr"     "package:purrr"    
# [7] "package:readr"     "package:tidyr"     "package:tibble"   
# [10] "package:ggplot2"   "package:tidyverse" "tools:rstudio"    
# [13] "package:stats"     "package:graphics"  "package:grDevices"
# [16] "package:utils"     "package:datasets"  "package:methods"  
# [19] "Autoloads"         "package:base"

功能：

move_pkg_env <- function(env, at, after = FALSE){
  if(is.numeric(env)) env <- search()[env]
  if(!startsWith(env, "package:"))
    stop("env must be a 'package::*' environment")
  if(!env %in% search())
    stop(paste(env,"is not on the search path"))

  pkg <- sub('package:','',env)
  pos <- which(env == search())[1]
  if(is.character(at)){
    at = which(at == search())[1]
    if(is.na(at)) stop(paste(pkg,"is not on the search path"))
  }
  detach(env,character.only = TRUE)
  at <- at + after - (pos < at)
  suppressWarnings(library(pkg,pos=at,
                           warn.conflicts = FALSE, 
                           quietly = TRUE,
                           character.only = TRUE,
                           verbose = FALSE))
}

move_env <- function(env, at, after = FALSE){
  if(is.numeric(env)) env <- search()[env]
  if(!env %in% search())
    stop(paste(env,"is not on the search path"))

  if(is.character(at)){
    at = which(at == search())[1]
    if(is.na(at)) stop(paste(pkg,"is not on the search path"))
  }
  at <- at + after

  pos <- which(env == search())[1]
  while(pos > at){
    move_pkg_env(pos-1,pos+1)
    pos <- which(env == search())[1] 
  }
  while(pos < at){
    move_pkg_env(pos+1,pos-1)
    pos <- which(env == search())[1] 
  }
}

【讨论】：