What happens when the following command is entered? help(ls(“package:MASS”)[92]) Use the observation to find out how many items there are in the package MASS.
help(ls) #透過help指令查閱ls的說明## starting httpd help server ... donels and objects return a vector of character strings giving the names of the objects in the specified environment. When invoked with no argument at the top level prompt, ls shows what data sets and functions a user has defined. When invoked with no argument inside a function, ls returns the names of the function’s local variables: this is useful in conjunction with browser.
library(MASS)
ls("package:MASS") ## [1] "abbey" "accdeaths" "addterm"
## [4] "Aids2" "Animals" "anorexia"
## [7] "area" "as.fractions" "bacteria"
## [10] "bandwidth.nrd" "bcv" "beav1"
## [13] "beav2" "biopsy" "birthwt"
## [16] "Boston" "boxcox" "cabbages"
## [19] "caith" "Cars93" "cats"
## [22] "cement" "chem" "con2tr"
## [25] "contr.sdif" "coop" "corresp"
## [28] "cov.mcd" "cov.mve" "cov.rob"
## [31] "cov.trob" "cpus" "crabs"
## [34] "Cushings" "DDT" "deaths"
## [37] "denumerate" "dose.p" "drivers"
## [40] "dropterm" "eagles" "enlist"
## [43] "epil" "eqscplot" "farms"
## [46] "fbeta" "fgl" "fitdistr"
## [49] "forbes" "fractions" "frequency.polygon"
## [52] "GAGurine" "galaxies" "gamma.dispersion"
## [55] "gamma.shape" "gehan" "genotype"
## [58] "geyser" "gilgais" "ginv"
## [61] "glm.convert" "glm.nb" "glmmPQL"
## [64] "hills" "hist.FD" "hist.scott"
## [67] "housing" "huber" "hubers"
## [70] "immer" "Insurance" "is.fractions"
## [73] "isoMDS" "kde2d" "lda"
## [76] "ldahist" "leuk" "lm.gls"
## [79] "lm.ridge" "lmsreg" "lmwork"
## [82] "loglm" "loglm1" "logtrans"
## [85] "lqs" "lqs.formula" "ltsreg"
## [88] "mammals" "mca" "mcycle"
## [91] "Melanoma" "menarche" "michelson"
## [94] "minn38" "motors" "muscle"
## [97] "mvrnorm" "nclass.freq" "neg.bin"
## [100] "negative.binomial" "negexp.SSival" "newcomb"
## [103] "nlschools" "npk" "npr1"
## [106] "Null" "oats" "OME"
## [109] "painters" "parcoord" "petrol"
## [112] "phones" "Pima.te" "Pima.tr"
## [115] "Pima.tr2" "polr" "psi.bisquare"
## [118] "psi.hampel" "psi.huber" "qda"
## [121] "quine" "Rabbit" "rational"
## [124] "renumerate" "rlm" "rms.curv"
## [127] "rnegbin" "road" "rotifer"
## [130] "Rubber" "sammon" "select"
## [133] "Shepard" "ships" "shoes"
## [136] "shrimp" "shuttle" "Sitka"
## [139] "Sitka89" "Skye" "snails"
## [142] "SP500" "stdres" "steam"
## [145] "stepAIC" "stormer" "studres"
## [148] "survey" "synth.te" "synth.tr"
## [151] "theta.md" "theta.ml" "theta.mm"
## [154] "topo" "Traffic" "truehist"
## [157] "ucv" "UScereal" "UScrime"
## [160] "VA" "waders" "whiteside"
## [163] "width.SJ" "write.matrix" "wtloss"ls("package:MASS")[92] #列出第92個物件名稱## [1] "menarche"help(ls("package:MASS")[92])Age of Menarche in Warsaw Description Proportions of female children at various ages during adolescence who have reached menarche.
查到package:MASS第92個項目menarche的說明。
help不只可以查指令，甚至可以查到內建資料裡面的變項說明。