Data
PromptBeginner5 minmarkdownQuality: 24
- Formula interface (`aggregate(y ~ x
data
1
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23,801 skills indexed with the new KISS metadata standard.
Showing 24 of 23,801Categories: Data & Insights, Coding & Debugging, Communication, Creative, Data
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)).
0
Data
PromptBeginner5 minmarkdownQuality: 24
- For data frames
operates on whole rows. For lists
1
Data
PromptBeginner5 minmarkdownQuality: 28
- Result is always an array (even 1D)
class table. Convert to data frame with as.data.frame(tbl).
1
Data
PromptBeginner5 minmarkdownQuality: 24
- rbind on data frames matches columns by name
not position. Missing columns get NA.
1
Data
PromptBeginner5 minmarkdownQuality: 28
- cbind on data frames calls data.frame(...)
not cbind.matrix. Mixing matrices and data frames can give unexpected results.
1
Data
PromptBeginner5 minmarkdownQuality: 28
- Default by is `intersect(names(x)
names(y))` — can silently merge on unintended columns if data frames share column names.
1
Data
PromptBeginner5 minmarkdownQuality: 28
- Returns an array (not a data frame). Class info on return values is discarded (e.g.
Date objects become numeric).
1
Data
PromptBeginner5 minmarkdownQuality: 28
- On a data frame
apply coerces to matrix via as.matrix first — mixed types become character.
1
Data
PromptBeginner5 minmarkdownQuality: 28
- subset argument uses non-standard evaluation — column names are resolved in the data frame
which can silently pick up wrong variables in programmatic use. Use [ with explicit logic in functions.
1
Data
PromptBeginner5 minmarkdownQuality: 24
- Matrix indexing a data frame (`df[cbind(i
j)]`) coerces to matrix first — avoid.
1
Data
PromptBeginner5 minmarkdownQuality: 28
- Data frame [ with single column: `df[
1]` returns a vector (drop=TRUE default for columns)
1
Coding & Debugging
PromptBeginner5 minmarkdownQuality: 28
- Factor indexing: x[f] uses integer codes of factor f
not its character labels. Use x[as.character(f)] for label-based indexing.
0
Data
PromptBeginner5 minmarkdownQuality: 24
- `ts(data
start
1
Data
PromptBeginner5 minmarkdownQuality: 24
- `relist(flesh
skeleton) — flesh` is the flat data
1
Creative
PromptBeginner5 minmarkdownQuality: 28
- `tryCatch(expr
warning = function(w) {...}) catches the first warning and exits. Use withCallingHandlers + invokeRestart(muffleWarning)` to suppress warnings but continue.
0
Creative
PromptBeginner5 minmarkdownQuality: 24
- Reduce with init adds a starting value: `Reduce(f
x
0
Data
PromptBeginner5 minmarkdownQuality: 24
- Useful pattern: `do.call(rbind
listofdfs)` to combine a list of data frames.
1
Data
PromptBeginner5 minmarkdownQuality: 28
- io-and-text.md — Read when: read.table silently drops data or misparses columns
regex behaves differently than expected
1
Data
PromptBeginner5 minmarkdownQuality: 28
- visualization.md — Read when: par settings reset unexpectedly
layout/mfrow interaction is confusing
1
Data
PromptBeginner5 minmarkdownQuality: 28
- statistics.md — Read when: hypothesis test gives surprising result
need to choose correct p.adjust method
1
Data
PromptBeginner5 minmarkdownQuality: 28
- data-wrangling.md — Read when: subsetting returns wrong type
apply on data frame gives unexpected coercion
1
Data
PromptBeginner5 minmarkdownQuality: 24
fit <- aov(value ~ group
data = df)
1
Data
PromptBeginner5 minmarkdownQuality: 24
fit <- lm(y ~ x1 + x2
data = df)
0