General
PromptBeginner5 minmarkdownQuality: 28
- lengths(x) returns the length of each element of a list. Equivalent to `sapply(x
length)` but faster (implemented in C).
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Showing 24 of 129,145Categories: Creative, Data, General
General
PromptBeginner5 minmarkdownQuality: 24
- `Find(f
x) returns the first element where f(elem) is TRUE. Find(f
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General
PromptBeginner5 minmarkdownQuality: 24
- `Map(f
...) is a simple wrapper for mapply(f
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Creative
PromptBeginner5 minmarkdownQuality: 24
- Reduce with init adds a starting value: `Reduce(f
x
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General
PromptBeginner5 minmarkdownQuality: 24
- `Filter(f
x) keeps elements where f(elem) is TRUE. Unlike x[sapply(x
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General
PromptBeginner5 minmarkdownQuality: 24
- `Reduce(f
x
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General
PromptBeginner5 minmarkdownQuality: 24
- `Reduce(f
x
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General
PromptBeginner5 minmarkdownQuality: 24
- `Reduce(f
x) applies binary function f cumulatively: Reduce(+
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General
PromptBeginner5 minmarkdownQuality: 24
- `do.call(fun
args_list) — args` must be a list
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Data
PromptBeginner5 minmarkdownQuality: 24
- Useful pattern: `do.call(rbind
listofdfs)` to combine a list of data frames.
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General
PromptBeginner5 minmarkdownQuality: 24
Non-obvious behaviors
gotchas
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General
PromptBeginner5 minmarkdownQuality: 24
- Use stop()
warning()
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General
PromptBeginner5 minmarkdownQuality: 24
- `with(df
expr) avoids repeating df$` everywhere
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General
PromptBeginner5 minmarkdownQuality: 28
- misc-utilities.md — Read when: do.call behaves differently than direct call
need Reduce/Filter/Map
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General
PromptBeginner5 minmarkdownQuality: 28
- dates-and-system.md — Read when: Date/POSIXct conversion gives wrong day
time zones cause off-by-one
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Data
PromptBeginner5 minmarkdownQuality: 28
- io-and-text.md — Read when: read.table silently drops data or misparses columns
regex behaves differently than expected
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Data
PromptBeginner5 minmarkdownQuality: 28
- visualization.md — Read when: par settings reset unexpectedly
layout/mfrow interaction is confusing
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Data
PromptBeginner5 minmarkdownQuality: 28
- statistics.md — Read when: hypothesis test gives surprising result
need to choose correct p.adjust method
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Data
PromptBeginner5 minmarkdownQuality: 28
- data-wrangling.md — Read when: subsetting returns wrong type
apply on data frame gives unexpected coercion
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General
PromptBeginner5 minmarkdownQuality: 24
- modeling.md — Read when: formula syntax is confusing (I()
* vs :
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General
PromptBeginner5 minmarkdownQuality: 24
For deeper coverage
read the reference files in references/:
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General
PromptBeginner5 minmarkdownQuality: 24
Non-obvious behaviors
surprising defaults
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General
PromptBeginner5 minmarkdownQuality: 24
labels = c(low
med
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General
PromptBeginner5 minmarkdownQuality: 24
cbind(df1
df2) # bind columns (same rows)
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