forked from google/styleguide
-
Notifications
You must be signed in to change notification settings - Fork 0
/
Rguide.xml
447 lines (404 loc) · 16.2 KB
/
Rguide.xml
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
<?xml version="1.0"?>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
<link rel="stylesheet" type="text/css" href="styleguide.css"/>
<title>Google's R Style Guide</title>
</head>
<body>
<h1>Google's R Style Guide</h1>
<p>
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.
</p>
<h2>Summary: R Style Rules</h2>
<ol>
<li><a href="#filenames">File Names</a>: end in <code>.R</code></li>
<li><a href="#identifiers">Identifiers</a>: <code>variable.name</code>
(or <code>variableName</code>),
<code>FunctionName</code>, <code>kConstantName</code></li>
<li><a href="#linelength">Line Length</a>: maximum 80 characters</li>
<li><a href="#indentation">Indentation</a>: two spaces, no tabs</li>
<li><a href="#spacing">Spacing</a></li>
<li><a href="#curlybraces">Curly Braces</a>: first on same line, last on
own line</li>
<li><a href="#else">else</a>: Surround else with braces </li>
<li><a href="#assignment">Assignment</a>: use <code><-</code>, not
<code>=</code></li>
<li><a href="#semicolons">Semicolons</a>: don't use them</li>
<li><a href="#generallayout"> General Layout and Ordering</a></li>
<li><a href="#comments"> Commenting Guidelines</a>: all comments begin
with <code>#</code> followed by a space; inline comments need two
spaces before the <code>#</code></li>
<li><a href="#functiondefinition">Function Definitions and Calls</a></li>
<li><a href="#functiondocumentation"> Function Documentation</a></li>
<li><a href="#examplefunction"> Example Function</a></li>
<li><a href="#todo"> TODO Style</a>: <code>TODO(username)</code></li>
</ol>
<h2>Summary: R Language Rules</h2>
<ol>
<li><a href="#attach"> <code>attach</code></a>: avoid using it</li>
<li><a href="#functionlanguage"> Functions</a>:
errors should be raised using <code>stop()</code></li>
<li><a href="#object"> Objects and Methods</a>: avoid S4 objects and
methods when possible; never mix S3 and S4 </li>
</ol>
<h3>Notation and Naming</h3>
<h4 id="filenames">File Names</h4>
<p>
File names should end in <code>.R</code> and, of course, be
meaningful.
<br/> GOOD: <code>predict_ad_revenue.R</code>
<br/> BAD: <code><span style="color:red">foo.R</span></code>
</p>
<h4 id="identifiers">Identifiers</h4>
<p>
Don't use underscores ( <code>_</code> ) or hyphens
( <code>-</code> ) 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
(<code>variable.name</code>), but <code>variableName</code>
is also accepted;
function names have initial capital letters and no dots
(<code>FunctionName</code>);
constants are named like functions but with an initial
<code>k</code>.
</p>
<ul>
<li><code>variable.name</code> is preferred, <code>variableName</code> is accepted
<br/> GOOD: <code>avg.clicks</code>
<br/> OK: <code>avgClicks</code>
<br/> BAD: <code><span style="color:red">avg_Clicks</span></code>
</li>
<li><code>FunctionName </code>
<br/> GOOD: <code>CalculateAvgClicks</code>
<br/> BAD: <code><span style="color:red">calculate_avg_clicks
</span></code>,
<code><span style="color:red">calculateAvgClicks</span></code>
<br/> Make function names verbs.
<br/><em>Exception: When creating a classed object, the function
name (constructor) and class should match (e.g., lm).</em></li>
<li><code>kConstantName </code></li>
</ul>
<h3>Syntax</h3>
<h4 id="linelength">Line Length</h4>
<p>
The maximum line length is 80 characters.
</p>
<h4 id="indentation">Indentation</h4>
<p>
When indenting your code, use two spaces. Never use tabs or mix
tabs and spaces.
<br/><em>Exception: When a line break occurs inside parentheses,
align the wrapped line with the first character inside the
parenthesis.</em>
</p>
<h4 id="spacing">Spacing</h4>
<p>
Place spaces around all binary operators (<code>=</code>,
<code>+</code>, <code>-</code>, <code><-</code>, etc.).
<br/><em> Exception: Spaces around <code>=</code>'s are
optional when passing parameters in a function call.</em>
</p>
<p>
Do not place a space before a comma, but always place one after a
comma.
<br/><br/> GOOD:
</p>
<pre>tab.prior <- table(df[df$days.from.opt < 0, "campaign.id"])
total <- sum(x[, 1])
total <- sum(x[1, ])</pre>
<p>
BAD:
</p>
<pre><span style="color:red">tab.prior <- table(df[df$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</span>
</pre>
<p>
Place a space before left parenthesis, except in a function call.
</p>
<p>
GOOD:
<br/><code>if (debug)</code>
</p>
<p>
BAD:
<br/><code><span style="color:red">if(debug)</span></code>
</p>
<p>
Extra spacing (i.e., more than one space in a row) is okay if it
improves alignment of equals signs or arrows (<code><-</code>).
</p>
<pre>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 = "")))
</pre>
<p>
Do not place spaces around code in parentheses or square brackets.
<br/><em> Exception: Always place a space after a comma.</em>
</p>
<p>
GOOD:</p><pre>if (debug)
x[1, ]</pre>
<p>
BAD:</p><pre><span style="color:red">if ( debug ) # No spaces around debug
x[1,] # Needs a space after the comma </span></pre>
<h4 id="curlybraces">Curly Braces</h4>
<p>
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 <em>consistently</em> either use or not use curly braces for
single statement blocks.
</p>
<pre>
if (is.null(ylim)) {
ylim <- c(0, 0.06)
}</pre>
<p>
xor (but not both)
</p>
<pre>
if (is.null(ylim))
ylim <- c(0, 0.06)</pre>
<p>
Always begin the body of a block on a new line.
</p>
<p>
BAD:
<br/><code><span style="color:red"> if (is.null(ylim))
ylim <- c(0, 0.06)</span></code>
<br/><code><span style="color:red"> if (is.null(ylim))
{ylim <- c(0, 0.06)} </span></code>
</p>
<h4 id="else">Surround else with braces</h4>
<p>
An <code>else</code> statement should always be surrounded on the
same line by curly braces.</p>
<pre>
if (condition) {
one or more lines
} else {
one or more lines
}
</pre>
<p>
BAD:<br/>
</p>
<pre style="color:red">
if (condition) {
one or more lines
}
else {
one or more lines
}
</pre>
<p>
BAD:<br/>
</p>
<pre style="color:red">
if (condition)
one line
else
one line
</pre>
<h4 id="assignment">Assignment</h4>
<p>
Use <code><-</code>, not <code>=</code>, for assignment.
</p>
<p>
GOOD:
<br/><code> x <- 5 </code>
</p>
<p>
BAD:
<br/><code><span style="color:red"> x = 5</span></code>
</p>
<h4 id="semicolons">Semicolons</h4>
<p>
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.)
</p>
<h3> Organization </h3>
<h4 id="generallayout">General Layout and Ordering</h4>
<p>
If everyone uses the same general ordering, we'll be able to
read and understand each other's scripts faster and more easily.
</p>
<ol>
<li>Copyright statement comment </li>
<li>Author comment</li>
<li>File description comment, including purpose of
program, inputs, and outputs</li>
<li><code>source()</code> and <code>library()</code> statements</li>
<li>Function definitions</li>
<li>Executed statements, if applicable (e.g.,
<code> print</code>, <code>plot</code>)</li>
</ol>
<p>
Unit tests should go in a separate file named
<code>originalfilename_test.R</code>.
</p>
<h4 id="comments">Commenting Guidelines</h4>
<p>
Comment your code. Entire commented lines should begin with
<code>#</code> and one space.
</p>
<p>
Short comments can be placed after code preceded by two spaces,
<code>#</code>, and then one space.
</p>
<pre># 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)")
</pre>
<h4 id="functiondefinition">Function Definitions and
Calls</h4>
<p>
Function definitions should first list arguments without default
values, followed by those with default values.
</p>
<p>
In both function definitions and function calls, multiple
arguments per line are allowed; line breaks are only allowed
between assignments.
<br/>GOOD:
</p>
<pre>PredictCTR <- function(query, property, num.days,
show.plot = TRUE)
</pre>
BAD:
<pre><span style="color:red">PredictCTR <- function(query, property, num.days, show.plot =
TRUE)
</span></pre>
<p> Ideally, unit tests should serve as sample function calls (for
shared library routines).
</p>
<h4 id="functiondocumentation">Function Documentation</h4>
<p> 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 <code>Args:</code>, with a description of
each (including the data type); and a description of the return
value, denoted by <code>Returns:</code>. The comments should be
descriptive enough that a caller can use the function without
reading any of the function's code.
</p>
<h4 id="examplefunction">Example Function</h4>
<pre>
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)
}
</pre>
<h4 id="todo">TODO Style</h4>
<p>
Use a consistent style for TODOs throughout your code.
<br/><code>TODO(username): Explicit description of action to
be taken</code>
</p>
<h3> Language </h3>
<h4 id="attach">Attach</h4>
<p> The possibilities for creating errors when using
<code>attach</code> are numerous. Avoid it.</p>
<h4 id="functionlanguage">Functions</h4>
<p> Errors should be raised using <code>stop()</code>.</p>
<h4 id="object">Objects and Methods</h4>
<p> 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:
<a href="http://cran.r-project.org/doc/Rnews/Rnews_2004-1.pdf">
http://cran.r-project.org/doc/Rnews/Rnews_2004-1.pdf</a>.)
</p>
<p>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.
</p>
<p>Avoid mixing S3 and S4: S4 methods ignore S3 inheritance and
vice-versa.
</p>
<h3>Exceptions</h3>
<p>
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.
</p>
<h3>Parting Words</h3>
<p>
Use common sense and BE CONSISTENT.
</p>
<p>
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
<code>if </code>
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.
</p>
<p>
The point of having style guidelines is to have a common vocabulary of
coding so people can concentrate on <em>what</em> you are saying,
rather than on <em>how</em> 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.
</p>
<p>
OK, enough writing about writing code; the code itself is much more
interesting. Have fun!
</p>
<h3>References</h3>
<p>
<a href="http://www.maths.lth.se/help/R/RCC/">
http://www.maths.lth.se/help/R/RCC/</a> - R Coding Conventions
</p>
<p>
<a href="http://ess.r-project.org/">http://ess.r-project.org/</a> - For
emacs users. This runs R in your emacs and has an emacs mode.
</p>
</body>
</html>