Compute a sequence of about `n+1`

equally spaced ‘round’
values which cover the range of the values in `x`

.
The values are chosen so that they are 1, 2 or 5 times a power of 10.

`pretty(x, …)`# S3 method for default
pretty(x, n = 5, min.n = n %/% 3, shrink.sml = 0.75,
high.u.bias = 1.5, u5.bias = .5 + 1.5*high.u.bias,
eps.correct = 0, …)

x

an object coercible to numeric by `as.numeric`

.

n

integer giving the *desired* number of
intervals. Non-integer values are rounded down.

min.n

nonnegative integer giving the *minimal* number of
intervals. If `min.n == 0`

, `pretty(.)`

may return a
single value.

shrink.sml

positive number, a factor (smaller than one)
by which a default scale is shrunk in the case when
`range(x)`

is very small (usually 0).

high.u.bias

non-negative numeric, typically \(> 1\).
The interval unit is determined as {1,2,5,10} times `b`

, a
power of 10. Larger `high.u.bias`

values favor larger units.

u5.bias

non-negative numeric
multiplier favoring factor 5 over 2. Default and ‘optimal’:
`u5.bias = .5 + 1.5*high.u.bias`

.

eps.correct

integer code, one of {0,1,2}. If non-0, an
*epsilon correction* is made at the boundaries such that
the result boundaries will be outside `range(x)`

; in the
*small* case, the correction is only done if ```
eps.correct
>= 2
```

.

…

further arguments for methods.

`pretty`

ignores non-finite values in `x`

.

Let `d <- max(x) - min(x)`

\(\ge 0\).
If `d`

is not (very close) to 0, we let `c <- d/n`

,
otherwise more or less `c <- max(abs(range(x)))*shrink.sml / min.n`

.
Then, the *10 base* `b`

is
\(10^{\lfloor{\log_{10}(c)}\rfloor}\) such
that \(b \le c < 10b\).

Now determine the basic *unit* \(u\) as one of
\(\{1,2,5,10\} b\), depending on
\(c/b \in [1,10)\)
and the two ‘*bias*’ coefficients, \(h
=\)`high.u.bias`

and \(f =\)`u5.bias`

.

………

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988)
*The New S Language*.
Wadsworth & Brooks/Cole.

`axTicks`

for the computation of pretty axis tick
locations in plots, particularly on the log scale.

# NOT RUN { pretty(1:15) # 0 2 4 6 8 10 12 14 16 pretty(1:15, h = 2) # 0 5 10 15 pretty(1:15, n = 4) # 0 5 10 15 pretty(1:15 * 2) # 0 5 10 15 20 25 30 pretty(1:20) # 0 5 10 15 20 pretty(1:20, n = 2) # 0 10 20 pretty(1:20, n = 10) # 0 2 4 ... 20 for(k in 5:11) { cat("k=", k, ": "); print(diff(range(pretty(100 + c(0, pi*10^-k)))))} ##-- more bizarre, when min(x) == max(x): pretty(pi) add.names <- function(v) { names(v) <- paste(v); v} utils::str(lapply(add.names(-10:20), pretty)) utils::str(lapply(add.names(0:20), pretty, min.n = 0)) sapply( add.names(0:20), pretty, min.n = 4) pretty(1.234e100) pretty(1001.1001) pretty(1001.1001, shrink = 0.2) for(k in -7:3) cat("shrink=", formatC(2^k, width = 9),":", formatC(pretty(1001.1001, shrink.sml = 2^k), width = 6),"\n") # }