Generazione di numeri pseudo-casuali

Campionamento in R

Richie Cotton

Data Evangelist at DataCamp

Cosa significa "random"?

Fatto, eseguito, che accade o scelto senza metodo o decisione consapevole.

Generati da processi fisici, come il lancio di una moneta.
Hotbits usa il decadimento radioattivo.
RANDOM.ORG usa il rumore atmosferico.
- Disponibile in R tramite il pacchetto random.
La vera casualità è costosa.

¹ https://www.fourmilab.ch/hotbits ² https://www.random.org

seed <- 1
calc_next_random(seed)

calc_next_random(3)

calc_next_random(2)

function	distribution	function	distribution	function	distribution
rbeta	Beta	rgeom	Geometric	rsignrank	Wilcoxon signed rank
rbinom	Binomial	rhyper	Hypergeometric	rt	t
rcauchy	Cauchy	rlnorm	Lognormal	runif	Uniform
rchisq	Chi-squared	rlogis	Logistic	rweibull	Weibull
rexp	Exponential	rnbinom	Negative binomial	rwilcox	Wilcoxon rank sum
rf	F	rnorm	Normal
rgamma	Gamma	rpois	Poisson

rbeta(5000, shape1 = 2, shape2 = 2)

[1] 0.2788 0.7495 0.6485 0.6665 0.6546 0.1575
...

[4996] 0.84719 0.35177 0.92796 0.67603 0.53960

randoms <- data.frame(
  beta = rbeta(5000, shape1 = 2, shape2 = 2)
)

ggplot(randoms, aes(beta)) +
  geom_histogram(binwidth = 0.1)

istogramma beta

set.seed(20000229)

rnorm(5)

-1.6538 -0.4028 -0.1654 -0.0734  0.5171

rnorm(5)

1.908  0.379 -1.499  1.625  0.693

set.seed(20000229)

rnorm(5)

-1.6538 -0.4028 -0.1654 -0.0734  0.5171

rnorm(5)

1.908  0.379 -1.499  1.625  0.693

set.seed(20000229)

rnorm(5)

-1.6538 -0.4028 -0.1654 -0.0734  0.5171

rnorm(5)

1.908  0.379 -1.499  1.625  0.693

set.seed(20041004)

rnorm(5)

-0.6547 -0.7854 -0.0152  0.1514  0.5285

rnorm(5)

0.748  0.974  0.174 -0.781 -0.930

Campionamento in R