Knowledge Quiz: Tutorial 1

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Which command sorts the numeric vector x in descending order using only base R?

sort(x)sort(x, decreasing = TRUE)sort(x, reverse = TRUE)sort(-x)order(x, decreasing = TRUE)

• FALSE. sort(x) sorts in ascending order by default.
• TRUE. sort(x, decreasing = TRUE) correctly sorts x in descending order.
• FALSE. sort(x, reverse = TRUE) is not a valid argument in the sort function.
• FALSE. sort(-x) sorts the negated values of x, which does not yield the correct descending order of x.
• FALSE. order(x, decreasing = TRUE) returns the indices that would sort x in descending order, not the sorted vector itself.

Suppose you have

{. .cell-code} y <- data.frame(x1 = 1:10, x2 = c(-1, 1), x3 = runif(10))

Which of the following commands sort the rows by x3 in ascending order (same result, possibly using different syntaxes)?

arrange(y, x3)arrange(y, +x3)y[order(y$x3, decreasing = FALSE), ]y[order(x3), ]arrange(y, -x3)

• TRUE. arrange(y, x3) sorts the data frame y by the column x3 in ascending order.
• TRUE. arrange(y, +x3) also sorts y by x3 in ascending order; the + sign does not change the order.
• TRUE. y[order(y$x3, decreasing = FALSE), ] sorts the rows of y by x3 in ascending order.
• FALSE. y[order(x3), ] will result in an error because x3 is not defined in the global environment; it needs to be referenced as y$x3.
• FALSE. arrange(y, -x3) sorts y by x3 in descending order, which is not what we want.