General
PromptBeginner5 minmarkdown
- `Find(f
x)` returns the **first** element where `f(elem)` is `TRUE`. `Find(f
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x)` returns the **first** element where `f(elem)` is `TRUE`. `Find(f
x)` returns the **index** of the first match (like `Find` but returns position
...)` is a simple wrapper for `mapply(f
x
x)` keeps elements where `f(elem)` is `TRUE`. Unlike `x[sapply(x
x
x
x)` applies binary function `f` cumulatively: `Reduce(+
args_list)` — `args` must be a **list**
gotchas
expr)` avoids repeating `df$` everywhere
`warning()`
need Reduce/Filter/Map
time zones cause off-by-one
`*` vs `:`
read the reference files in `references/`:
surprising defaults
med
breaks = c(0
df2) # stack rows (same columns)
df2) # bind columns (same rows)
]
]
-df$value)