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Exercise

Data frames and matrices - column selection

All values in a matrix must have the same data type, which has efficiency implications when selecting rows and columns.

Suppose we have two objects, mat (a matrix) and df (a data frame).

Instructions

100 XP

Using the microbenchmark() function, how long does it take to select the first column from each of these object? In other words, which is faster mat[, 1] or df[, 1]?