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
x)` keeps elements where `f(elem)` is `TRUE`. Unlike `x[sapply(x
x)` applies binary function `f` cumulatively: `Reduce(+
x
args_list)` — `args` must be a **list**
gotchas
expr)` avoids repeating `df$` everywhere
need Reduce/Filter/Map
`warning()`
time zones cause off-by-one
`*` vs `:`
surprising defaults
read the reference files in `references/`:
med
breaks = c(0
df2) # bind columns (same rows)
df2) # stack rows (same columns)
]
-df$value)
]
] # descending
v2))
] # ascending