Exercise 5: R matrix operations

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.

  FUN <- function(x) {
    return(apply(x, MARGIN = 1, FUN = median))
  }

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