BootstraParalelo.R

data(cars)
fit = lm(dist ~ speed, data=cars)
summary(fit)

system.time({
  nBoot = 10000
  coefs = rep(NA, nBoot)
  for (j in 1:nBoot){
    i = sample(nrow(cars), replace = TRUE)
    fitBoot = lm(dist ~ speed, data=cars[i,])
    coefs[j] = coef(fitBoot)[2]
  }
})

hist(coefs)
qs = quantile(coefs, c(.025, .975))
sapply(qs, function(x) abline(v=x, lwd=2, col=2))




## Versao paralela
## Passo 1: utilizar conteudo do for()
## Passo 2: criar uma funcao com o conteudo acima
## Passo 3: funcao retornar o valor de interesse
meuBoot = function(cars){
  i = sample(nrow(cars), replace = TRUE)
  fitBoot = lm(dist ~ speed, data=cars[i,])
  return(coef(fitBoot))
}

library(foreach)
library(doMPI)
## informar numero de processadores
registerDoMC(2)


results = foreach(j=1:10000, .combine=cbind) %dopar% {
    meuBoot(cars)
}