+ 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,
+ 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.
+ Variable names should have all lower case letters and words
+ separated with dots (.);
+ function names have initial capital letters and no dots
+ (CapWords);
+ constants are named like functions but with an initial
+ k.
+
variable.name
+ avg.clicks
+ avg_Clicks
+ , avgClicks
+
+
+ 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:
tabPrior <- table(df[df$daysFromOpt < 0, "campaignid"])
+total <- sum(x[, 1])
+total <- sum(x[1, ])+ BAD:
tabPrior <- table(df[df$daysFromOpt<0, "campaignid"]) # Needs spaces around '<'
+tabPrior <- table(df[df$daysFromOpt < 0,"campaignid"]) # Needs a space after the comma
+tabPrior<- table(df[df$daysFromOpt < 0, "campaignid"]) # Needs a space before <-
+tabPrior<-table(df[df$daysFromOpt < 0, "campaignid"]) # 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 = xCoord,
+ y = dataMat[, 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)}
+
+ 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_unittest.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$pctSpent,
+ 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, numDays,
+ showPlot = TRUE)
+PredictCTR <- function(query, property, numDays, showPlot =
+ 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 invalid 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: + + http://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. +
+ 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! + + +