- R is a high-level programming language used primarily for - statistical computing and graphics. The goal of the R - Programming Style Guide is to make our R code easier to read, - share, and verify. The rules below were designed in - collaboration with the entire R user community at Google. - -
- - - - - - -.Rvariable.name
- (or variableName),
- FunctionName, kConstantName<-, not
- =# followed by a space; inline comments need two
- spaces before the #TODO(username)attach: avoid using itstop()
- File names should end in .R and, of course, be
- meaningful.
-
GOOD: predict_ad_revenue.R
-
BAD: foo.R
-
- Don't use underscores ( _ ) or hyphens
- ( - ) in identifiers.
- Identifiers should be named according to the following conventions.
- The preferred form for variable names is all lower case
- letters and words separated with dots
- (variable.name), but variableName
- is also accepted;
- function names have initial capital letters and no dots
- (FunctionName);
- constants are named like functions but with an initial
- k.
-
variable.name is preferred, variableName is accepted
- avg.clicks
- avgClicks
- avg_Clicks
- FunctionName
- CalculateAvgClicks
- calculate_avg_clicks
- ,
- calculateAvgClicks
- kConstantName - The maximum line length is 80 characters. -
- -
- When indenting your code, use two spaces. Never use tabs or mix
- tabs and spaces.
-
Exception: When a line break occurs inside parentheses,
- align the wrapped line with the first character inside the
- parenthesis.
-
- Place spaces around all binary operators (=,
- +, -, <-, etc.).
-
Exception: Spaces around ='s are
- optional when passing parameters in a function call.
-
- Do not place a space before a comma, but always place one after a
- comma.
-
GOOD:
-
tab.prior <- table(df[df$days.from.opt < 0, "campaign.id"]) -total <- sum(x[, 1]) -total <- sum(x[1, ])-
- BAD: -
-tab.prior <- table(df[df$days.from.opt<0, "campaign.id"]) # Needs spaces around '<'
-tab.prior <- table(df[df$days.from.opt < 0,"campaign.id"]) # Needs a space after the comma
-tab.prior<- table(df[df$days.from.opt < 0, "campaign.id"]) # Needs a space before <-
-tab.prior<-table(df[df$days.from.opt < 0, "campaign.id"]) # Needs spaces around <-
-total <- sum(x[,1]) # Needs a space after the comma
-total <- sum(x[ ,1]) # Needs a space after the comma, not before
-
- - Place a space before left parenthesis, except in a function call. -
-
- GOOD:
- if (debug)
-
- BAD:
- if(debug)
-
- Extra spacing (i.e., more than one space in a row) is okay if it
- improves alignment of equals signs or arrows (<-).
-
plot(x = x.coord, - y = data.mat[, MakeColName(metric, ptiles[1], "roiOpt")], - ylim = ylim, - xlab = "dates", - ylab = metric, - main = (paste(metric, " for 3 samples ", sep = ""))) --
- Do not place spaces around code in parentheses or square brackets.
-
Exception: Always place a space after a comma.
-
- GOOD:
if (debug) -x[1, ]-
- BAD:
if ( debug ) # No spaces around debug
-x[1,] # Needs a space after the comma
-
- - An opening curly brace should never go on its own line; a closing - curly brace should always go on its own line. You may omit curly - braces when a block consists of a single statement; however, you - must consistently either use or not use curly braces for - single statement blocks. -
-
-if (is.null(ylim)) {
- ylim <- c(0, 0.06)
-}
- - xor (but not both) -
--if (is.null(ylim)) - ylim <- c(0, 0.06)-
- Always begin the body of a block on a new line. -
-
- BAD:
- if (is.null(ylim))
- ylim <- c(0, 0.06)
- if (is.null(ylim))
- {ylim <- c(0, 0.06)}
-
- An else statement should always be surrounded on the
- same line by curly braces.
-if (condition) {
- one or more lines
-} else {
- one or more lines
-}
-
-
- BAD:
-
-if (condition) {
- one or more lines
-}
-else {
- one or more lines
-}
-
-
- BAD:
-
-if (condition) - one line -else - one line -- -
- Use <-, not =, for assignment.
-
- GOOD:
- x <- 5
-
- BAD:
- x = 5
-
- Do not terminate your lines with semicolons or use semicolons to - put more than one command on the same line. (Semicolons are not - necessary, and are omitted for consistency with other Google style - guides.) -
- - -- If everyone uses the same general ordering, we'll be able to - read and understand each other's scripts faster and more easily. -
-source() and library() statements print, plot)
- Unit tests should go in a separate file named
- originalfilename_test.R.
-
- Comment your code. Entire commented lines should begin with
- # and one space.
-
- Short comments can be placed after code preceded by two spaces,
- #, and then one space.
-
# Create histogram of frequency of campaigns by pct budget spent. -hist(df$pct.spent, - breaks = "scott", # method for choosing number of buckets - main = "Histogram: fraction budget spent by campaignid", - xlab = "Fraction of budget spent", - ylab = "Frequency (count of campaignids)") --
- Function definitions should first list arguments without default - values, followed by those with default values. -
-
- In both function definitions and function calls, multiple
- arguments per line are allowed; line breaks are only allowed
- between assignments.
-
GOOD:
-
PredictCTR <- function(query, property, num.days, - show.plot = TRUE) -- BAD: -
PredictCTR <- function(query, property, num.days, show.plot =
- TRUE)
-
- Ideally, unit tests should serve as sample function calls (for - shared library routines). -
- Functions should contain a comments section immediately below
- the function definition line. These comments should consist of a
- one-sentence description of the function; a list of the function's
- arguments, denoted by Args:, with a description of
- each (including the data type); and a description of the return
- value, denoted by Returns:. The comments should be
- descriptive enough that a caller can use the function without
- reading any of the function's code.
-
-CalculateSampleCovariance <- function(x, y, verbose = TRUE) {
- # Computes the sample covariance between two vectors.
- #
- # Args:
- # x: One of two vectors whose sample covariance is to be calculated.
- # y: The other vector. x and y must have the same length, greater than one,
- # with no missing values.
- # verbose: If TRUE, prints sample covariance; if not, not. Default is TRUE.
- #
- # Returns:
- # The sample covariance between x and y.
- n <- length(x)
- # Error handling
- if (n <= 1 || n != length(y)) {
- stop("Arguments x and y have different lengths: ",
- length(x), " and ", length(y), ".")
- }
- if (TRUE %in% is.na(x) || TRUE %in% is.na(y)) {
- stop(" Arguments x and y must not have missing values.")
- }
- covariance <- var(x, y)
- if (verbose)
- cat("Covariance = ", round(covariance, 4), ".\n", sep = "")
- return(covariance)
-}
-
-
-
- Use a consistent style for TODOs throughout your code.
- TODO(username): Explicit description of action to
- be taken
-
The possibilities for creating errors when using
- attach are numerous. Avoid it.
Errors should be raised using stop().
The S language has two object systems, S3 and S4, both of which - are available in R. S3 methods are more interactive and flexible, - whereas S4 methods are more formal and rigorous. (For an illustration - of the two systems, see Thomas Lumley's - "Programmer's Niche: A Simple - Class, in S3 and S4" in R News 4/1, 2004, pgs. 33 - 36: - - https://cran.r-project.org/doc/Rnews/Rnews_2004-1.pdf.) -
-Use S3 objects and methods unless there is a strong reason to use - S4 objects or methods. A primary justification for an S4 object - would be to use objects directly in C++ code. A primary - justification for an S4 generic/method would be to dispatch on two - arguments. -
-Avoid mixing S3 and S4: S4 methods ignore S3 inheritance and - vice-versa. -
- - -- The coding conventions described above should be followed, unless - there is good reason to do otherwise. Exceptions include legacy - code and modifying third-party code. -
- - -- Use common sense and BE CONSISTENT. -
-
- If you are editing code, take a few minutes to look at the code around
- you and determine its style. If others use spaces around their
- if
- clauses, you should, too. If their comments have little boxes of stars
- around them, make your comments have little boxes of stars around them,
- too.
-
- The point of having style guidelines is to have a common vocabulary of - coding so people can concentrate on what you are saying, - rather than on how you are saying it. We present global style - rules here so people - know the vocabulary. But local style is also important. If code you add - to a file looks drastically different from the existing code around it, - the discontinuity will throw readers out of their rhythm when they go to - read it. Try to avoid this. -
- -- OK, enough writing about writing code; the code itself is much more - interesting. Have fun! -
- - -- - http://www.maths.lth.se/help/R/RCC/ - R Coding Conventions -
-- http://ess.r-project.org/ - For - emacs users. This runs R in your emacs and has an emacs mode. -
- - - -