Question

Which of the following finds row sums for each level of a grouping variable?

(a) as.numeric(x)

(b) rowsum(x, group, reorder = TRUE, …)

(c) as.order(x)

(d) colSums (x, na.rm = FALSE, dims = 1)

The question was posed to me in examination.

This is a very interesting question from Commands in portion Commands, Packages, Visualizing Data and Linear Regression of R Programming

Answer 1

Correct choice is (b) rowsum(x, group, reorder = TRUE, …)

Explanation: rowsum compute column sums across rows of a numeric matrix-like object for each level of a grouping variable.