8:27
help.search (which does the same as ??)
RSiteSearch
%/%
all.equal(x, pi) or, even better, isTRUE(all.equal(x, pi))
At least two of the following:
<-
assign
Inf and -Inf
0, Inf, and -Inf
numeric, integer, and complex
nlevels
as.numeric("6.283185")
summary, head, str, unclass, attributes, or View. Bonus points if you’ve discovered tail, the counterpart to head that prints the last few rows.
rm(list = ls())
seq.int(0, 1, 0.25)
name = value pairs when the vector is created, or by calling the names function afterward.
3 * 4 * 5 = 60
%*%
3. The inner list counts as one element, and so does the NULL element.
formals, or in the global environment variable .Options.
$) operator.
Thirdly, you can call the subset function.
check.names = FALSE to data.frame.
rbind for appending vertically or cbind for appending horizontally.
list2env is the best solution, but as.environment also works.
formals, args, and formalArgs.
do.call calls a function with its arguments in a list form.
format, formatC, sprintf, and prettyNum are the main ones.
alarm, or printing an \a character to the console.
factor and ordered
NA).
cut to bin it.
if will throw an error if you pass NA to it.
ifelse will return NA values in the corresponding positions where NA is passed to it.
switch will conditionally execute code based upon a character or integer argument.
break into your loop code.
next into your loop code.
lapply, vapply, sapply, apply, mapply, and tapply were all discussed in the chapter, with eapply and rapply getting brief mentions too. Try apropos("apply") to see all of them.
lapply always returns a list, vapply always returns a vector or array as specified by a template, and sapply can return either.
rapply is recursive, and ideal for deeply nested objects like trees.
tapply (or something from the plyr package).
**ply, the first asterisk denotes the type of the first input argument and the second asterisk denotes the type of the return value.
library throws an error if it fails, whereas require returns a logical value (letting you do custom error handling).
.libPaths returns a list of libraries.
POSIXct classes must be used. Dates don’t store the time information, and POSIXlt dates store their data as lists, which won’t fit inside a data frame.
"%B %Y"
x<-Sys.time()x+3600
## [1] "2013-07-17 22:44:55 BST"
60 * 60 * 24 * 365 seconds. A period of one year will be 366 days in a leap year.
data function with no arguments.
read.csv assumes that a decimal place is represented by a full stop (period) and that each item is separated by a comma, whereas read.csv2 assumes that a decimal place is represented by a comma and that each item is separated by a semicolon. read.csv is used for data created in locales where a period is used as a decimal place (most English-speaking locales, for example). read.csv2 is for data created in locales where a comma is used (most European locales, for example). If you are unsure, simply open your data file in a text editor.
read.xlsx2 from the xlsx package is a good first choice, but there is also read.xlsx in the same package, and different functions in several other packages.
read.csv, or use download.file to get a local copy.
readLines, call str_count to count the number of instances in each line, and sum the total.
with, within, transform, and mutate all allow manipulating columns and adding columns to data frames, as well as standard assignment.
order or arrange.
TRUE when you have a positive number—for example, is.positive <- function(x) x > 0—and call Find(is.positive, x).
min returns the single smallest value of all its inputs. pmin accepts several vectors that are the same length, and returns the smallest at each point along them.
pch (“plot character”) argument.
y ~ x.
set.seed), generate the numbers, then reset the seed to the same value.
d, followed by the name of the distribution. For example, the PDF for the binomial distribution is dbinom. CDF functions start with p followed by the name of the distribution, and inverse CDF functions begin with q followed by the name of the distribution.
anova, AIC, and BIC are common functions for comparing models.
summary(model)$r.squared.
warnings function shows the previous warnings.
try returns an object of class try-error.
testthat equivalent of checkException is expect_exception. Say that 10 times fast.
quote turns a string into a call, then eval evaluates it.
print.foo will be called for objects of class foo.
roxygenise or roxygenize
.Deprecated. Later, replace the body completely with a call to .Defunct.