General
PromptBeginner5 minmarkdown
- **dates-and-system.md** — Read when: Date/POSIXct conversion gives wrong day
time zones cause off-by-one
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General
PromptBeginner5 minmarkdown
- **modeling.md** — Read when: formula syntax is confusing (`I()`
`*` vs `:`
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General
PromptBeginner5 minmarkdown
For deeper coverage
read the reference files in `references/`:
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General
PromptBeginner5 minmarkdown
Non-obvious behaviors
surprising defaults
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General
PromptBeginner5 minmarkdown
labels = c(low
med
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General
PromptBeginner5 minmarkdown
df$category <- cut(df$value
breaks = c(0
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General
PromptBeginner5 minmarkdown
rbind(df1
df2) # stack rows (same columns)
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PromptBeginner5 minmarkdown
cbind(df1
df2) # bind columns (same rows)
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df[!duplicated(df$id)
]
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PromptBeginner5 minmarkdown
df[!duplicated(df)
]
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df[order(df$group
-df$value)
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PromptBeginner5 minmarkdown
df[order(-df$value)
] # descending
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General
PromptBeginner5 minmarkdown
df[order(df$value)
] # ascending
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PromptBeginner5 minmarkdown
varying = list(c(v1
v2))
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General
PromptBeginner5 minmarkdown
idvar = id
timevar = time
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wide <- reshape(long
direction = wide
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long <- reshape(wide
direction = long
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General
PromptBeginner5 minmarkdown
merged <- merge(df1
df2
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General
PromptBeginner5 minmarkdown
merged <- merge(df1
df2
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PromptBeginner5 minmarkdown
merged <- merge(df1
df2
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PromptBeginner5 minmarkdown
cor.test(x
y
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General
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chisq.test(table(df$a
df$b))
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General
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t.test(x
mu = 0) # one-sample
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General
PromptBeginner5 minmarkdown
t.test(x
y) # two-sample
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