In msperlin/adfeR: Data, exercises and Functions for Book "Analise de Dados Financeiros e Economicos com o R"

x <- 1:50
y <- 50:1

# solution using `base`
z <- (y - c(NA, x[1:(length(x)-1)]))/c(NA, NA, y[1:(length(y)-2)])

# solution with tidyverse (much prettier huh!)
z <- (y - lag(x, n = 1))/lag(y, n = 2)

# solution (be aware of the NA values)
my_sol <- sum(z, na.rm = TRUE)

my_answers <- make_random_answers(my_sol)

#check_answers(my_answers)

Question

Crie um vetor $z_i$ de acordo com a fórmula a seguir onde $x_i=1...50$ e $y_i=50...1$. Qual é o valor da soma dos elementos de $z_i$? Dica: veja o funcionamento da função dplyr::lag.

$$ z_i=\frac{y_i - x_{i-1}}{y_{i-2}} $$

exams::answerlist(my_answers, markup = "markdown")

Solution

Meta-information

extype: schoice exsolution: r mchoice2string(c(TRUE, FALSE, FALSE, FALSE, FALSE), single = TRUE) exname: "numeric " exshuffle: TRUE

msperlin/adfeR documentation built on March 26, 2021, 3:05 a.m.