Exercise 5: R matrix operations
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Find a function FUN that leads to the following output:
a <- matrix(1:36, nrow = 6) b <- matrix(1:25, nrow = 5) a ## [,1] [,2] [,3] [,4] [,5] [,6] ## [1,] 1 7 13 19 25 31 ## [2,] 2 8 14 20 26 32 ## [3,] 3 9 15 21 27 33 ## [4,] 4 10 16 22 28 34 ## [5,] 5 11 17 23 29 35 ## [6,] 6 12 18 24 30 36 FUN(a) ## [1] 16 17 18 19 20 21 b ## [,1] [,2] [,3] [,4] [,5] ## [1,] 1 6 11 16 21 ## [2,] 2 7 12 17 22 ## [3,] 3 8 13 18 23 ## [4,] 4 9 14 19 24 ## [5,] 5 10 15 20 25 FUN(b) ## [1] 11 12 13 14 15
Hint: aim to keep the answer simple. The main logic of the function can often be summarized in a single line of R code.
Answer: click to reveal
We can write the function as follows:
FUN <- function(x) {
return(apply(x, MARGIN = 1, FUN = median))
}
This function computes the median for each row of the input matrix.
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