previdencia.r

pay_taxes <- function(income, brackets){
  # for each bracket, subtract x reais from income
  taxes_total <- 0
  income_left <- income
  
  for(i in 1:nrow(brackets)){
    # get taxed reais and tax rate
    reais_taxed <- brackets[i,]$reais - 
      ifelse(i==1,0,brackets[i-1,]$reais)
    
    rate_of_tax <- brackets[i,]$tax_rate
    
    # if you're at the top marginal, reset the Inf to = remaining income
    reais_taxed <- ifelse(reais_taxed == Inf, income_left, reais_taxed)
    
    # if residual income <0, set taxed reais = remaining income
    reais_taxed <- ifelse(income_left - reais_taxed < 0, income_left, reais_taxed)
    
    # calculate taxes paid
    taxes_paid <- reais_taxed * rate_of_tax
    
    # calculate residual income
    taxes_total <- ifelse(income_left >= 0, taxes_total + taxes_paid, taxes_total)
    income_left <- income_left - reais_taxed
  }
  
  #return(data.frame(income,taxes_total,on_paper=rate_of_tax))
  return(taxes_total)
}

teste <- data.frame(SAL_CONTRIB = c(1163.55, 2000, 4000, 5000, 7000, 8000, 15000, 30000))

faixas <- data.frame(reais = c(1163.55,2000,3000,5839.45,10000,20000, Inf),
                     tax_rate = c(7.5, 9, 12, 14, 14.5, 16.5, 19)/100)

teste$imposto <- pay_taxes(teste$SAL_CONTRIB, faixas)

#  pay_taxes(teste$SAL_CONTRIB[8], faixas) == 4833.35
#  teste$imposto[8] == 2933.35