Search Path - R Programming

The search path records attached packages, but package workflows are clearer when important calls are written with explicit namespaces.
Program

Play the script to choose a package and build the qualified call that avoids search-path ambiguity.
                            package_index
                            package_index = 2 (default)package_index = 1package_index = 3
                        

                            search_path_plan.R
                        
Replay: real traced execution (multi-file project)

                            search_path <- c("package:stats", "package:graphics", "package:utils")
package_index <- 2
chosen <- c("stats", "graphics", "utils")[package_index]
functions <- c(stats = "median", graphics = "plot", utils = "head")
qualified <- paste0(chosen, "::", functions[[chosen]])
already_attached <- paste0("package:", chosen) %in% search_path
label <- paste(qualified, already_attached, sep = "=")
cat(label, "\n", sep = "")
search_path <- c("package:stats", "package:graphics", "package:utils")
package_index <- 1
chosen <- c("stats", "graphics", "utils")[package_index]
functions <- c(stats = "median", graphics = "plot", utils = "head")
qualified <- paste0(chosen, "::", functions[[chosen]])
already_attached <- paste0("package:", chosen) %in% search_path
label <- paste(qualified, already_attached, sep = "=")
cat(label, "\n", sep = "")
search_path <- c("package:stats", "package:graphics", "package:utils")
package_index <- 3
chosen <- c("stats", "graphics", "utils")[package_index]
functions <- c(stats = "median", graphics = "plot", utils = "head")
qualified <- paste0(chosen, "::", functions[[chosen]])
already_attached <- paste0("package:", chosen) %in% search_path
label <- paste(qualified, already_attached, sep = "=")
cat(label, "\n", sep = "")

                        
1search_path ← package:stats, package:graphics, package:utils1search_path <- c("package:stats", "package:graphics", "package:utils")2package_index <- 2⋯values this steppackage:stats, package:graphics, package:utilssearch_path
2package_index ← 21search_path <- c("package:stats", "package:graphics", "package:utils")2package_index <- 23chosen <- c("stats", "graphics", "utils")[package_index]⋯values this step2package_index
3chosen ← graphics⋯2package_index <- 23chosen <- c("stats", "graphics", "utils")[package_index]4functions <- c(stats = "median", graphics = "plot", utils = "head")⋯values this stepgraphicschosen2package_index
4functions ← stats=median, graphics=plot, utils=head⋯3chosen <- c("stats", "graphics", "utils")[package_index]4functions <- c(stats = "median", graphics = "plot", utils = "head")5qualified <- paste0(chosen, "::", functions[[chosen]])⋯values this stepstats=median, graphics=plot, utils=headfunctions
5qualified ← graphics::plot⋯4functions <- c(stats = "median", graphics = "plot", utils = "head")5qualified <- paste0(chosen, "::", functions[[chosen]])6already_attached <- paste0("package:", chosen) %in% search_path⋯values this stepgraphics::plotqualifiedgraphicschosenplotfunctions[[chosen]]
6already_attached ← TRUE⋯5qualified <- paste0(chosen, "::", functions[[chosen]])6already_attached <- paste0("package:", chosen) %in% search_path7label <- paste(qualified, already_attached, sep = "=")⋯values this stepTRUEalready_attachedgraphicschosen3 entriessearch_path
7label ← graphics::plot=TRUE⋯6already_attached <- paste0("package:", chosen) %in% search_path7label <- paste(qualified, already_attached, sep = "=")8cat(label, "\n", sep = "")values this stepgraphics::plot=TRUElabelgraphics::plotqualifiedTRUEalready_attached
8cat(label, " ", sep = "")⋯7label <- paste(qualified, already_attached, sep = "=")8cat(label, "\n", sep = "")outputgraphics::plot=TRUEvalues this stepgraphics::plot=TRUElabel
1search_path ← package:stats, package:graphics, package:utils1search_path <- c("package:stats", "package:graphics", "package:utils")2package_index <- 1⋯values this steppackage:stats, package:graphics, package:utilssearch_path
2package_index ← 11search_path <- c("package:stats", "package:graphics", "package:utils")2package_index <- 13chosen <- c("stats", "graphics", "utils")[package_index]⋯values this step1package_index
3chosen ← stats⋯2package_index <- 13chosen <- c("stats", "graphics", "utils")[package_index]4functions <- c(stats = "median", graphics = "plot", utils = "head")⋯values this stepstatschosen1package_index
4functions ← stats=median, graphics=plot, utils=head⋯3chosen <- c("stats", "graphics", "utils")[package_index]4functions <- c(stats = "median", graphics = "plot", utils = "head")5qualified <- paste0(chosen, "::", functions[[chosen]])⋯values this stepstats=median, graphics=plot, utils=headfunctions
5qualified ← stats::median⋯4functions <- c(stats = "median", graphics = "plot", utils = "head")5qualified <- paste0(chosen, "::", functions[[chosen]])6already_attached <- paste0("package:", chosen) %in% search_path⋯values this stepstats::medianqualifiedstatschosenmedianfunctions[[chosen]]
6already_attached ← TRUE⋯5qualified <- paste0(chosen, "::", functions[[chosen]])6already_attached <- paste0("package:", chosen) %in% search_path7label <- paste(qualified, already_attached, sep = "=")⋯values this stepTRUEalready_attachedstatschosen3 entriessearch_path
7label ← stats::median=TRUE⋯6already_attached <- paste0("package:", chosen) %in% search_path7label <- paste(qualified, already_attached, sep = "=")8cat(label, "\n", sep = "")values this stepstats::median=TRUElabelstats::medianqualifiedTRUEalready_attached
8cat(label, " ", sep = "")⋯7label <- paste(qualified, already_attached, sep = "=")8cat(label, "\n", sep = "")outputstats::median=TRUEvalues this stepstats::median=TRUElabel
1search_path ← package:stats, package:graphics, package:utils1search_path <- c("package:stats", "package:graphics", "package:utils")2package_index <- 3⋯values this steppackage:stats, package:graphics, package:utilssearch_path
2package_index ← 31search_path <- c("package:stats", "package:graphics", "package:utils")2package_index <- 33chosen <- c("stats", "graphics", "utils")[package_index]⋯values this step3package_index
3chosen ← utils⋯2package_index <- 33chosen <- c("stats", "graphics", "utils")[package_index]4functions <- c(stats = "median", graphics = "plot", utils = "head")⋯values this steputilschosen3package_index
4functions ← stats=median, graphics=plot, utils=head⋯3chosen <- c("stats", "graphics", "utils")[package_index]4functions <- c(stats = "median", graphics = "plot", utils = "head")5qualified <- paste0(chosen, "::", functions[[chosen]])⋯values this stepstats=median, graphics=plot, utils=headfunctions
5qualified ← utils::head⋯4functions <- c(stats = "median", graphics = "plot", utils = "head")5qualified <- paste0(chosen, "::", functions[[chosen]])6already_attached <- paste0("package:", chosen) %in% search_path⋯values this steputils::headqualifiedutilschosenheadfunctions[[chosen]]
6already_attached ← TRUE⋯5qualified <- paste0(chosen, "::", functions[[chosen]])6already_attached <- paste0("package:", chosen) %in% search_path7label <- paste(qualified, already_attached, sep = "=")⋯values this stepTRUEalready_attachedutilschosen3 entriessearch_path
7label ← utils::head=TRUE⋯6already_attached <- paste0("package:", chosen) %in% search_path7label <- paste(qualified, already_attached, sep = "=")8cat(label, "\n", sep = "")values this steputils::head=TRUElabelutils::headqualifiedTRUEalready_attached
8cat(label, " ", sep = "")⋯7label <- paste(qualified, already_attached, sep = "=")8cat(label, "\n", sep = "")outpututils::head=TRUEvalues this steputils::head=TRUElabel
search path `search()` reports attached packages; this example models that list as data.
namespace `qualified` stores a package-qualified function name.
membership `%in%` checks whether the chosen package is attached.