From 228a8ef7d09944ac7a4646ff5cfbb811f49926ec Mon Sep 17 00:00:00 2001 From: "mshields@google.com" Date: Thu, 18 Jul 2013 23:41:50 +0000 Subject: [PATCH] Restore r105 of Rguide.xml, now with the svn:mime-type property set. --- Rguide.xml | 447 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 447 insertions(+) create mode 100644 Rguide.xml diff --git a/Rguide.xml b/Rguide.xml new file mode 100644 index 0000000..add76d3 --- /dev/null +++ b/Rguide.xml @@ -0,0 +1,447 @@ + + + + + + Google's R Style Guide + + + + +

Google's R Style Guide

+ +

+ 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. + +

+ + + + + + +

Summary: R Style Rules

+ +
    +
  1. File Names: end in .R
    2. +
  2. Identifiers: variable.name + (or variableName), + FunctionName, kConstantName
    3. +
  3. Line Length: maximum 80 characters
    4. +
  4. Indentation: two spaces, no tabs
    5. +
  5. Spacing
    6. +
  6. Curly Braces: first on same line, last on + own line
    7. +
  7. else: Surround else with braces
    8. +
  8. Assignment: use <-, not + =
    9. +
  9. Semicolons: don't use them
    10. +
  10. General Layout and Ordering
    11. +
  11. Commenting Guidelines: all comments begin + with # followed by a space; inline comments need two + spaces before the #
    12. +
  12. Function Definitions and Calls
    13. +
  13. Function Documentation
    14. +
  14. Example Function
    15. +
  15. TODO Style: TODO(username)
    16. +
+ +

Summary: R Language Rules

+
    +
  1. attach: avoid using it
    2. +
  2. Functions: + errors should be raised using stop()
    3. +
  3. Objects and Methods: avoid S4 objects and + methods when possible; never mix S3 and S4
    4. +
+ +

Notation and Naming

+ +

File Names

+

+ File names should end in .R and, of course, be + meaningful. +
GOOD: predict_ad_revenue.R +
BAD: foo.R +

+ +

Identifiers

+

+ 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. +

+ + + +

Syntax

+ +

Line Length

+

+ The maximum line length is 80 characters. +

+ +

Indentation

+

+ 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. +

+ +

Spacing

+

+ 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
+ +

Curly Braces

+

+ 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)} +

+ +

Surround else with braces

+

+ 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
+
+ +

Assignment

+

+ Use <-, not =, for assignment. +

+

+ GOOD: +
x <- 5 +

+

+ BAD: +
x = 5 +

+

Semicolons

+

+ 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.) +

+ + +

Organization

+

General Layout and Ordering

+

+ If everyone uses the same general ordering, we'll be able to + read and understand each other's scripts faster and more easily. +

+
    +
  1. Copyright statement comment
    2. +
  2. Author comment
    3. +
  3. File description comment, including purpose of + program, inputs, and outputs
    4. +
  4. source() and library() statements
    5. +
  5. Function definitions
    6. +
  6. Executed statements, if applicable (e.g., + print, plot)
    7. +
+

+ Unit tests should go in a separate file named + originalfilename_test.R. +

+

Commenting Guidelines

+

+ 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 and + Calls

+

+ 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). +

+

Function Documentation

+

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. +

+ +

Example Function

+
+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)
+}
+
+ +

TODO Style

+ +

+ Use a consistent style for TODOs throughout your code. +
TODO(username): Explicit description of action to + be taken +

+ + +

Language

+ +

Attach

+

The possibilities for creating errors when using + attach are numerous. Avoid it.

+

Functions

+

Errors should be raised using stop().

+

Objects and Methods

+

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. +

+ + +

Exceptions

+ +

+ 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. +

+ + +

Parting Words

+ +

+ 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! +

+ + +

References

+ +

+ + 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. +

+ + + +