README.md
In leeper/lookfor: Find What You're Looking For
lookfor: Find what you're looking for
lookfor is an R port of Stata's lookfor command, which helps you find stuff you're looking for inside a dataset (e.g., variables, variable values, variable labels, etc.).
Package Installation
The latest development version on GitHub can be installed using devtools:
if(!require("devtools")){
install.packages("devtools")
library("devtools")
}
install_github("leeper/lookfor")
Examples
Stata's lookfor command searches variables and variable labels for an exact matching text string:
. webuse auto
(1978 Automobile Data)
. lookfor weight
storage display value
variable name type format label variable label
---------------------------------------------------------------------
weight int %8.0gc Weight (lbs.)
. lookfor ft
storage display value
variable name type format label variable label
---------------------------------------------------------------------
trunk int %8.0g Trunk space (cu. ft.)
turn int %8.0g Turn Circle (ft.)
This is helpful and something easily replicated by searching within the names attribute of a data.frame. But R allows multiple objects to be present at one time, meaning that it would be time consuming to grep the names of all data.frames that might be active in memory at any given point in time. Similarly, those R objects are also themselves named, have numerous other attributes (rownames, colnames, levels, class, etc.), and might be stored within lists or environments. While the lookfor command in Stata is helpful, it's actually solving a relatively simple problem. Porting lookfor to R requires a much more robust solution for searching many different features of potentially numerous data objects stored in various parts of the R environment.
The major weakness of Stata's lookfor command is that it relies only on a plain text, exact matching search algorithm. This makes it difficult to search for variables or labels that match a pattern (e.g., a pattern that might easily be described by a regular expression). As a result, the R port uses grepl to find matches, meaning that regular expressions are used by default when trying to find something and arguments can be passed via ... to control the behavior of grepl (e.g., setting fixed=TRUE will match an exact string, and perl=TRUE will use Perl-style regular expressions).
Look in a data.frame
options(width = 100)
A basic use case is to search for an observation or a variable within a dataset.
library("lookfor")
data(USArrests)
# look for observation
lookin(USArrests, "Alaska")
## [1] Matches found for 'Alaska' in attributes(USArrests):
## $names
##
## $class
##
## $row.names
## Object Position Match
## X[[i]] 2 Alaska
# look for variable
lookin(USArrests, "Assault")
## [1] Matches found for 'Assault' in attributes(USArrests):
## $names
## Object Position Match
## X[[i]] 2 Assault
##
## $class
##
## $row.names
Look in an environment
Relatedly, it is possible to search for objects within an environment (and values or attributes within those objects).
x <- new.env()
x$mtcars <- mtcars
x$cars <- letters[1:10]
x$cards <- 1:5
lookin(x, "car")
## [1] Matches found for 'car' in attributes(mtcars):
## $names
## Object Position Match
## X[[i]] 11 carb
##
## $row.names
##
## $class
Look in a list
And the same can be applied to a potentially deeply nested list.
m <- lm(mpg ~ cyl, data = mtcars)
lookin(m, "mpg")
## Error in setNames(w, x[w]): attempt to apply non-function
Look everywhere
Lastly, the lookfor command can be used to look anywhere (within .GlobalEnv, the R search path, objects within objects on the search path, loaded namespaces, etc.).
lookfor("package")
## lookfor found matches for 'package' in the following locations...
##
## Objects on search() path:
## Position in search()
## package:lookfor 2
## package:stats 3
## package:graphics 4
## package:grDevices 5
## package:utils 6
## package:datasets 7
## package:base 9
##
## Objects from Namespaces:
## Namespace Object Position in Namespace
## [1,] tools check_packages_in_dir 33
## [2,] tools check_packages_in_dir_changes 34
## [3,] tools check_packages_in_dir_details 35
## [4,] tools check_packages_in_dir_results 36
## [5,] tools check_packages_in_dir_results_summary 37
## [6,] tools CRAN_package_db 73
## [7,] tools format.check_code_usage_in_package 110
## [8,] tools format.check_package_code_assign_to_globalenv 116
## [9,] tools format.check_package_code_attach 117
## [10,] tools format.check_package_code_data_into_globalenv 118
## [11,] tools format.check_package_code_startup_functions 119
## [12,] tools format.check_package_code_unload_functions 120
## [13,] tools format.check_package_CRAN_incoming 121
## [14,] tools format.check_package_datasets 122
## [15,] tools format.check_package_depends 123
## [16,] tools format.check_package_description_encoding 124
## [17,] tools format.check_package_description2 125
## [18,] tools format.check_package_license 126
## [19,] tools format.check_packages_in_dir_changes 127
## [20,] tools format.check_packages_used 128
## [21,] tools package.dependencies 221
## [22,] tools package_dependencies 222
## [23,] tools print.check_package_code_syntax 273
## [24,] tools print.check_package_compact_datasets 274
## [25,] tools print.check_package_description 275
## [26,] tools print.check_packages_in_dir 276
## [27,] tools print.check_packages_in_dir_changes 277
## [28,] tools Rd_package_author 317
## [29,] tools Rd_package_description 318
## [30,] tools Rd_package_DESCRIPTION 319
## [31,] tools Rd_package_indices 320
## [32,] tools Rd_package_maintainer 321
## [33,] tools Rd_package_title 322
## [34,] tools summarize_check_packages_in_dir_depends 384
## [35,] tools summarize_check_packages_in_dir_results 385
## [36,] tools summarize_check_packages_in_dir_timings 386
## [37,] tools summary.check_packages_in_dir 389
## [38,] tools toHTML.packageIQR 408
## [39,] tools url_db_from_installed_packages 418
## [40,] tools url_db_from_package_citation 419
## [41,] tools url_db_from_package_HTML_files 420
## [42,] tools url_db_from_package_metadata 421
## [43,] tools url_db_from_package_news 422
## [44,] tools url_db_from_package_Rd_db 423
## [45,] tools url_db_from_package_README_md 424
## [46,] tools url_db_from_package_sources 425
## [47,] utils aspell_control_package_vignettes 32
## [48,] utils aspell_package 41
## [49,] utils aspell_package_C_files 42
## [50,] utils aspell_package_description 43
## [51,] utils aspell_package_pot_files 44
## [52,] utils aspell_package_R_files 45
## [53,] utils aspell_package_Rd_files 46
## [54,] utils aspell_package_vignettes 47
## [55,] utils available.packages 57
## [56,] utils available_packages_filters_db 58
## [57,] utils available_packages_filters_default 59
## [58,] utils CRAN.packages 152
## [59,] utils download.packages 166
## [60,] utils filter_packages_by_depends_predicates 181
## [61,] utils install.packages 248
## [62,] utils installed.packages 249
## [63,] utils make.packages.html 261
## [64,] utils new.packages 280
## [65,] utils old.packages 285
## [66,] utils package.skeleton 286
## [67,] utils packageDescription 287
## [68,] utils packageName 288
## [69,] utils packageStatus 289
## [70,] utils packageVersion 290
## [71,] utils print.packageDescription 313
## [72,] utils print.packageIQR 314
## [73,] utils print.packageStatus 315
## [74,] utils print.summary.packageStatus 320
## [75,] utils remove.packages 354
## [76,] utils summary.packageStatus 411
## [77,] utils update.packages 448
## [78,] utils update.packageStatus 449
## [79,] utils upgrade.packageStatus 451
## [80,] knitr has_package 93
## [81,] methods packageSlot 196
## [82,] methods packageSlot<- 197
## [83,] base $.package_version 11
## [84,] base as.package_version 211
## [85,] base find.package 450
## [86,] base format.packageInfo 474
## [87,] base is.package_version 587
## [88,] base package_version 765
## [89,] base packageEvent 766
## [90,] base packageHasNamespace 767
## [91,] base packageStartupMessage 768
## [92,] base path.package 779
## [93,] base print.packageInfo 816
##
Look using regular expression
As noted above, Stata's lookfor command can only match exact/partial character strings. The R port by uses grepl, meaning that regular expressions are supported by default, thus allowing for complex pattern matching.
data(mtcars)
# Look for car names containing letters and numbers (anywhere)
lookfor("[[:alpha:]]+ [[:digit:]]")
## lookfor found matches for '[[:alpha:]]+ [[:digit:]]' in the following locations...
##
## Within objects from global environment:
## $coefficients
##
## $residuals
##
## $effects
##
## $rank
##
## $fitted.values
##
## $assign
##
## $qr
## $qr
##
## $qraux
##
## $pivot
##
## $tol
##
## $rank
##
## [[1]]
##
## [[2]]
##
##
## $df.residual
##
## $xlevels
##
## $call
## $values
## integer(0)
##
## attr(,"location")
## [1] "values"
## attr(,"class")
## [1] "lookin"
## attr(,"object")
## [1] "X[[i]]"
## attr(,"what")
## [1] "[[:alpha:]]+ [[:digit:]]"
##
## $terms
## $values
## integer(0)
##
## attr(,"location")
## [1] "values"
## attr(,"class")
## [1] "lookin"
## attr(,"object")
## [1] "X[[i]]"
## attr(,"what")
## [1] "[[:alpha:]]+ [[:digit:]]"
##
## $model
## [1] Matches found for '[[:alpha:]]+ [[:digit:]]' in attributes(X[[i]]):
## $names
##
## $terms
## $values
## integer(0)
##
## attr(,"location")
## [1] "values"
## attr(,"class")
## [1] "lookin"
## attr(,"object")
## [1] "X[[i]]"
## attr(,"what")
## [1] "[[:alpha:]]+ [[:digit:]]"
##
## $row.names
## Object Position Match
## X[[i]] 3 Datsun 710
## X[[i]] 4 Hornet 4 Drive
## X[[i]] 7 Duster 360
## X[[i]] 8 Merc 240D
## X[[i]] 9 Merc 230
## X[[i]] 10 Merc 280
## X[[i]] 11 Merc 280C
## X[[i]] 12 Merc 450SE
## X[[i]] 13 Merc 450SL
## X[[i]] 14 Merc 450SLC
## X[[i]] 18 Fiat 128
## X[[i]] 27 Porsche 914-2
## X[[i]] 32 Volvo 142E
##
## $class
##
##
## [[1]]
##
## [[2]]
##
## [1] Matches found for '[[:alpha:]]+ [[:digit:]]' in attributes(mtcars):
## $names
##
## $row.names
## Object Position Match
## X[[i]] 3 Datsun 710
## X[[i]] 4 Hornet 4 Drive
## X[[i]] 7 Duster 360
## X[[i]] 8 Merc 240D
## X[[i]] 9 Merc 230
## X[[i]] 10 Merc 280
## X[[i]] 11 Merc 280C
## X[[i]] 12 Merc 450SE
## X[[i]] 13 Merc 450SL
## X[[i]] 14 Merc 450SLC
## X[[i]] 18 Fiat 128
## X[[i]] 27 Porsche 914-2
## X[[i]] 32 Volvo 142E
##
## $class
##
## [1] Matches found for '[[:alpha:]]+ [[:digit:]]' in attributes(mtcars):
## $names
##
## $row.names
## Object Position Match
## X[[i]] 3 Datsun 710
## X[[i]] 4 Hornet 4 Drive
## X[[i]] 7 Duster 360
## X[[i]] 8 Merc 240D
## X[[i]] 9 Merc 230
## X[[i]] 10 Merc 280
## X[[i]] 11 Merc 280C
## X[[i]] 12 Merc 450SE
## X[[i]] 13 Merc 450SL
## X[[i]] 14 Merc 450SLC
## X[[i]] 18 Fiat 128
## X[[i]] 27 Porsche 914-2
## X[[i]] 32 Volvo 142E
##
## $class
##
# Look for car names containing letters and numbers (in mtcars)
lookin(mtcars, "[[:alpha:]]+ [[:digit:]]")
## [1] Matches found for '[[:alpha:]]+ [[:digit:]]' in attributes(mtcars):
## $names
##
## $row.names
## Object Position Match
## X[[i]] 3 Datsun 710
## X[[i]] 4 Hornet 4 Drive
## X[[i]] 7 Duster 360
## X[[i]] 8 Merc 240D
## X[[i]] 9 Merc 230
## X[[i]] 10 Merc 280
## X[[i]] 11 Merc 280C
## X[[i]] 12 Merc 450SE
## X[[i]] 13 Merc 450SL
## X[[i]] 14 Merc 450SLC
## X[[i]] 18 Fiat 128
## X[[i]] 27 Porsche 914-2
## X[[i]] 32 Volvo 142E
##
## $class
Search comment() values
R's comment() function is an underutilized feature that allows users to attach hidden comments to R objects. This is intended (see ? comment) for helping to annotate R objects with relevant metadata. The value of comment() for an object is NULL unless it has been set, in which case it is usually a character vector of length 1 (or possibly greater). lookfor searches comment() values automatically, allowing you to make better use of these annotations.
m1 <- lm(mpg ~ cyl, data = mtcars)
comment(m1) <- "model using continuous cylinder"
m2 <- lm(mpg ~ factor(cyl), data = mtcars)
comment(m2) <- "model using factor of cylinder"
lookfor("model using", fixed = TRUE)
## lookfor found matches for 'model using' in the following locations...
##
## Within objects from global environment:
## [1] Matches found for 'model using' in comment(x):
## function (..., recursive = FALSE) .Primitive("c")
## [1] Matches found for 'model using' in comment(x):
## function (..., recursive = FALSE) .Primitive("c")
##
leeper/lookfor documentation built on May 21, 2019, 12:37 a.m.
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Note that we can't provide technical support on individual packages. You should contact the package authors for that.
lookfor: Find what you're looking for
lookfor is an R port of Stata's lookfor command, which helps you find stuff you're looking for inside a dataset (e.g., variables, variable values, variable labels, etc.).
Package Installation
The latest development version on GitHub can be installed using devtools:
if(!require("devtools")){
install.packages("devtools")
library("devtools")
}
install_github("leeper/lookfor")
Examples
Stata's lookfor command searches variables and variable labels for an exact matching text string:
. webuse auto
(1978 Automobile Data)
. lookfor weight
storage display value
variable name type format label variable label
---------------------------------------------------------------------
weight int %8.0gc Weight (lbs.)
. lookfor ft
storage display value
variable name type format label variable label
---------------------------------------------------------------------
trunk int %8.0g Trunk space (cu. ft.)
turn int %8.0g Turn Circle (ft.)
This is helpful and something easily replicated by searching within the names attribute of a data.frame. But R allows multiple objects to be present at one time, meaning that it would be time consuming to grep the names of all data.frames that might be active in memory at any given point in time. Similarly, those R objects are also themselves named, have numerous other attributes (rownames, colnames, levels, class, etc.), and might be stored within lists or environments. While the lookfor command in Stata is helpful, it's actually solving a relatively simple problem. Porting lookfor to R requires a much more robust solution for searching many different features of potentially numerous data objects stored in various parts of the R environment.
The major weakness of Stata's lookfor command is that it relies only on a plain text, exact matching search algorithm. This makes it difficult to search for variables or labels that match a pattern (e.g., a pattern that might easily be described by a regular expression). As a result, the R port uses grepl to find matches, meaning that regular expressions are used by default when trying to find something and arguments can be passed via ... to control the behavior of grepl (e.g., setting fixed=TRUE will match an exact string, and perl=TRUE will use Perl-style regular expressions).
Look in a data.frame
options(width = 100)
A basic use case is to search for an observation or a variable within a dataset.
library("lookfor")
data(USArrests)
# look for observation
lookin(USArrests, "Alaska")
## [1] Matches found for 'Alaska' in attributes(USArrests):
## $names
##
## $class
##
## $row.names
## Object Position Match
## X[[i]] 2 Alaska
# look for variable
lookin(USArrests, "Assault")
## [1] Matches found for 'Assault' in attributes(USArrests):
## $names
## Object Position Match
## X[[i]] 2 Assault
##
## $class
##
## $row.names
Look in an environment
Relatedly, it is possible to search for objects within an environment (and values or attributes within those objects).
x <- new.env()
x$mtcars <- mtcars
x$cars <- letters[1:10]
x$cards <- 1:5
lookin(x, "car")
## [1] Matches found for 'car' in attributes(mtcars):
## $names
## Object Position Match
## X[[i]] 11 carb
##
## $row.names
##
## $class
Look in a list
And the same can be applied to a potentially deeply nested list.
m <- lm(mpg ~ cyl, data = mtcars)
lookin(m, "mpg")
## Error in setNames(w, x[w]): attempt to apply non-function
Look everywhere
Lastly, the lookfor command can be used to look anywhere (within .GlobalEnv, the R search path, objects within objects on the search path, loaded namespaces, etc.).
lookfor("package")
## lookfor found matches for 'package' in the following locations...
##
## Objects on search() path:
## Position in search()
## package:lookfor 2
## package:stats 3
## package:graphics 4
## package:grDevices 5
## package:utils 6
## package:datasets 7
## package:base 9
##
## Objects from Namespaces:
## Namespace Object Position in Namespace
## [1,] tools check_packages_in_dir 33
## [2,] tools check_packages_in_dir_changes 34
## [3,] tools check_packages_in_dir_details 35
## [4,] tools check_packages_in_dir_results 36
## [5,] tools check_packages_in_dir_results_summary 37
## [6,] tools CRAN_package_db 73
## [7,] tools format.check_code_usage_in_package 110
## [8,] tools format.check_package_code_assign_to_globalenv 116
## [9,] tools format.check_package_code_attach 117
## [10,] tools format.check_package_code_data_into_globalenv 118
## [11,] tools format.check_package_code_startup_functions 119
## [12,] tools format.check_package_code_unload_functions 120
## [13,] tools format.check_package_CRAN_incoming 121
## [14,] tools format.check_package_datasets 122
## [15,] tools format.check_package_depends 123
## [16,] tools format.check_package_description_encoding 124
## [17,] tools format.check_package_description2 125
## [18,] tools format.check_package_license 126
## [19,] tools format.check_packages_in_dir_changes 127
## [20,] tools format.check_packages_used 128
## [21,] tools package.dependencies 221
## [22,] tools package_dependencies 222
## [23,] tools print.check_package_code_syntax 273
## [24,] tools print.check_package_compact_datasets 274
## [25,] tools print.check_package_description 275
## [26,] tools print.check_packages_in_dir 276
## [27,] tools print.check_packages_in_dir_changes 277
## [28,] tools Rd_package_author 317
## [29,] tools Rd_package_description 318
## [30,] tools Rd_package_DESCRIPTION 319
## [31,] tools Rd_package_indices 320
## [32,] tools Rd_package_maintainer 321
## [33,] tools Rd_package_title 322
## [34,] tools summarize_check_packages_in_dir_depends 384
## [35,] tools summarize_check_packages_in_dir_results 385
## [36,] tools summarize_check_packages_in_dir_timings 386
## [37,] tools summary.check_packages_in_dir 389
## [38,] tools toHTML.packageIQR 408
## [39,] tools url_db_from_installed_packages 418
## [40,] tools url_db_from_package_citation 419
## [41,] tools url_db_from_package_HTML_files 420
## [42,] tools url_db_from_package_metadata 421
## [43,] tools url_db_from_package_news 422
## [44,] tools url_db_from_package_Rd_db 423
## [45,] tools url_db_from_package_README_md 424
## [46,] tools url_db_from_package_sources 425
## [47,] utils aspell_control_package_vignettes 32
## [48,] utils aspell_package 41
## [49,] utils aspell_package_C_files 42
## [50,] utils aspell_package_description 43
## [51,] utils aspell_package_pot_files 44
## [52,] utils aspell_package_R_files 45
## [53,] utils aspell_package_Rd_files 46
## [54,] utils aspell_package_vignettes 47
## [55,] utils available.packages 57
## [56,] utils available_packages_filters_db 58
## [57,] utils available_packages_filters_default 59
## [58,] utils CRAN.packages 152
## [59,] utils download.packages 166
## [60,] utils filter_packages_by_depends_predicates 181
## [61,] utils install.packages 248
## [62,] utils installed.packages 249
## [63,] utils make.packages.html 261
## [64,] utils new.packages 280
## [65,] utils old.packages 285
## [66,] utils package.skeleton 286
## [67,] utils packageDescription 287
## [68,] utils packageName 288
## [69,] utils packageStatus 289
## [70,] utils packageVersion 290
## [71,] utils print.packageDescription 313
## [72,] utils print.packageIQR 314
## [73,] utils print.packageStatus 315
## [74,] utils print.summary.packageStatus 320
## [75,] utils remove.packages 354
## [76,] utils summary.packageStatus 411
## [77,] utils update.packages 448
## [78,] utils update.packageStatus 449
## [79,] utils upgrade.packageStatus 451
## [80,] knitr has_package 93
## [81,] methods packageSlot 196
## [82,] methods packageSlot<- 197
## [83,] base $.package_version 11
## [84,] base as.package_version 211
## [85,] base find.package 450
## [86,] base format.packageInfo 474
## [87,] base is.package_version 587
## [88,] base package_version 765
## [89,] base packageEvent 766
## [90,] base packageHasNamespace 767
## [91,] base packageStartupMessage 768
## [92,] base path.package 779
## [93,] base print.packageInfo 816
##
Look using regular expression
As noted above, Stata's lookfor command can only match exact/partial character strings. The R port by uses grepl, meaning that regular expressions are supported by default, thus allowing for complex pattern matching.
data(mtcars)
# Look for car names containing letters and numbers (anywhere)
lookfor("[[:alpha:]]+ [[:digit:]]")
## lookfor found matches for '[[:alpha:]]+ [[:digit:]]' in the following locations...
##
## Within objects from global environment:
## $coefficients
##
## $residuals
##
## $effects
##
## $rank
##
## $fitted.values
##
## $assign
##
## $qr
## $qr
##
## $qraux
##
## $pivot
##
## $tol
##
## $rank
##
## [[1]]
##
## [[2]]
##
##
## $df.residual
##
## $xlevels
##
## $call
## $values
## integer(0)
##
## attr(,"location")
## [1] "values"
## attr(,"class")
## [1] "lookin"
## attr(,"object")
## [1] "X[[i]]"
## attr(,"what")
## [1] "[[:alpha:]]+ [[:digit:]]"
##
## $terms
## $values
## integer(0)
##
## attr(,"location")
## [1] "values"
## attr(,"class")
## [1] "lookin"
## attr(,"object")
## [1] "X[[i]]"
## attr(,"what")
## [1] "[[:alpha:]]+ [[:digit:]]"
##
## $model
## [1] Matches found for '[[:alpha:]]+ [[:digit:]]' in attributes(X[[i]]):
## $names
##
## $terms
## $values
## integer(0)
##
## attr(,"location")
## [1] "values"
## attr(,"class")
## [1] "lookin"
## attr(,"object")
## [1] "X[[i]]"
## attr(,"what")
## [1] "[[:alpha:]]+ [[:digit:]]"
##
## $row.names
## Object Position Match
## X[[i]] 3 Datsun 710
## X[[i]] 4 Hornet 4 Drive
## X[[i]] 7 Duster 360
## X[[i]] 8 Merc 240D
## X[[i]] 9 Merc 230
## X[[i]] 10 Merc 280
## X[[i]] 11 Merc 280C
## X[[i]] 12 Merc 450SE
## X[[i]] 13 Merc 450SL
## X[[i]] 14 Merc 450SLC
## X[[i]] 18 Fiat 128
## X[[i]] 27 Porsche 914-2
## X[[i]] 32 Volvo 142E
##
## $class
##
##
## [[1]]
##
## [[2]]
##
## [1] Matches found for '[[:alpha:]]+ [[:digit:]]' in attributes(mtcars):
## $names
##
## $row.names
## Object Position Match
## X[[i]] 3 Datsun 710
## X[[i]] 4 Hornet 4 Drive
## X[[i]] 7 Duster 360
## X[[i]] 8 Merc 240D
## X[[i]] 9 Merc 230
## X[[i]] 10 Merc 280
## X[[i]] 11 Merc 280C
## X[[i]] 12 Merc 450SE
## X[[i]] 13 Merc 450SL
## X[[i]] 14 Merc 450SLC
## X[[i]] 18 Fiat 128
## X[[i]] 27 Porsche 914-2
## X[[i]] 32 Volvo 142E
##
## $class
##
## [1] Matches found for '[[:alpha:]]+ [[:digit:]]' in attributes(mtcars):
## $names
##
## $row.names
## Object Position Match
## X[[i]] 3 Datsun 710
## X[[i]] 4 Hornet 4 Drive
## X[[i]] 7 Duster 360
## X[[i]] 8 Merc 240D
## X[[i]] 9 Merc 230
## X[[i]] 10 Merc 280
## X[[i]] 11 Merc 280C
## X[[i]] 12 Merc 450SE
## X[[i]] 13 Merc 450SL
## X[[i]] 14 Merc 450SLC
## X[[i]] 18 Fiat 128
## X[[i]] 27 Porsche 914-2
## X[[i]] 32 Volvo 142E
##
## $class
##
# Look for car names containing letters and numbers (in mtcars)
lookin(mtcars, "[[:alpha:]]+ [[:digit:]]")
## [1] Matches found for '[[:alpha:]]+ [[:digit:]]' in attributes(mtcars):
## $names
##
## $row.names
## Object Position Match
## X[[i]] 3 Datsun 710
## X[[i]] 4 Hornet 4 Drive
## X[[i]] 7 Duster 360
## X[[i]] 8 Merc 240D
## X[[i]] 9 Merc 230
## X[[i]] 10 Merc 280
## X[[i]] 11 Merc 280C
## X[[i]] 12 Merc 450SE
## X[[i]] 13 Merc 450SL
## X[[i]] 14 Merc 450SLC
## X[[i]] 18 Fiat 128
## X[[i]] 27 Porsche 914-2
## X[[i]] 32 Volvo 142E
##
## $class
Search comment() values
R's comment() function is an underutilized feature that allows users to attach hidden comments to R objects. This is intended (see ? comment) for helping to annotate R objects with relevant metadata. The value of comment() for an object is NULL unless it has been set, in which case it is usually a character vector of length 1 (or possibly greater). lookfor searches comment() values automatically, allowing you to make better use of these annotations.
m1 <- lm(mpg ~ cyl, data = mtcars)
comment(m1) <- "model using continuous cylinder"
m2 <- lm(mpg ~ factor(cyl), data = mtcars)
comment(m2) <- "model using factor of cylinder"
lookfor("model using", fixed = TRUE)
## lookfor found matches for 'model using' in the following locations...
##
## Within objects from global environment:
## [1] Matches found for 'model using' in comment(x):
## function (..., recursive = FALSE) .Primitive("c")
## [1] Matches found for 'model using' in comment(x):
## function (..., recursive = FALSE) .Primitive("c")
##
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