General
PromptBeginner5 minmarkdownQuality: 24
- system.time(expr) returns user
system
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General
PromptBeginner5 minmarkdownQuality: 24
- options(digits = n): significant digits for printing (1-22
default 7). Suggestion only.
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General
PromptBeginner5 minmarkdownQuality: 28
- options(scipen = n): positive biases toward fixed notation
negative toward scientific. Default 0. Applies to print/format/cat but not sprintf.
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General
PromptBeginner5 minmarkdownQuality: 24
- `as.numeric(diff
units = hours)` to extract numeric value in specific units.
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General
PromptBeginner5 minmarkdownQuality: 24
- `difftime(time1
time2
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General
PromptBeginner5 minmarkdownQuality: 24
- Explicit units: secs
mins
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General
PromptBeginner5 minmarkdownQuality: 24
- POSIXct: seconds since 1970-01-01 UTC (compact
a numeric vector).
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General
PromptBeginner5 minmarkdownQuality: 28
- difftime arithmetic: subtracting POSIXct objects gives difftime. Units auto-selected (secs
mins
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General
PromptBeginner5 minmarkdownQuality: 24
- POSIXlt: list with components $sec
$min
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General
PromptBeginner5 minmarkdownQuality: 24
Non-obvious behaviors
gotchas
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General
PromptBeginner5 minmarkdownQuality: 24
- `format(date
%Y)` for year
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General
PromptBeginner5 minmarkdownQuality: 24
- `seq.Date(from
to
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General
PromptBeginner5 minmarkdownQuality: 24
- Returns a permutation vector of indices
not the sorted values. Use x[order(x)] to sort.
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General
PromptBeginner5 minmarkdownQuality: 28
- For character sorting
depends on locale. Use method = radix for locale-independent fast sorting.
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General
PromptBeginner5 minmarkdownQuality: 24
- Default is ascending; use -x for descending numeric
or decreasing = TRUE.
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Data
PromptBeginner5 minmarkdownQuality: 24
- If FUN returns multiple values
result column is a matrix column inside the data frame.
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General
PromptBeginner5 minmarkdownQuality: 24
- Works on multiple arguments (e.g.
`complete.cases(x
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General
PromptBeginner5 minmarkdownQuality: 28
- Returns columns named after the grouping variables
with result column keeping the original name.
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Data
PromptBeginner5 minmarkdownQuality: 24
- Formula interface (`aggregate(y ~ x
data
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General
PromptBeginner5 minmarkdownQuality: 24
- c() on factors unions level sets (since R 4.1.0)
but earlier versions converted to integer.
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General
PromptBeginner5 minmarkdownQuality: 24
- Levels are sorted by default
but sort order is locale-dependent at creation time.
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General
PromptBeginner5 minmarkdownQuality: 28
- Only == and != work between factors; factors must have identical level sets. Ordered factors suppo...
.
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General
PromptBeginner5 minmarkdownQuality: 28
- Duplicate column names allowed only with check.names = FALSE
but many operations will de-dup them silently.
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Coding & Debugging
PromptBeginner5 minmarkdownQuality: 28
- as.numeric(f) returns integer codes
not original values. Use as.numeric(levels(f))[f] or as.numeric(as.character(f)).
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