**Exercise 1**

Create an array (3 dimensional) of 24 elements using the `dim()`

function.

**Exercise 2**

Create an array (3 dimensional) of 24 elements using the `array()`

function.

**Exercise 3**

Assign some dimnames of your choice to the array using the `dimnames()`

function.

**Exercise 4**

Assign some dimnames of your choice to the array using the arguments of the `array()`

function.

**Exercise 5**

Instead of column-major array, make a row-major array (transpose).

**Exercise 6**

For this exercise, and all that follow, download this file, and read it into R using the `read.csv()`

function, e.g.:

`temp`

Copy the column named `N`

into a new variable `arr`

.

**Exercise 7**

Set dimensions of this variable and convert it into a 3 * 2 * 4 array. Add dimnames.

**Exercise 8**

Print the whole array on the screen.

**Exercise 9**

Print only elements of height 2, assuming the first dimension represents rows, the second columns and the third heigth.

**Exercise 10**

Print elements of height 1 and columns 3 and 1.

**Exercise 11**

Print element of height 2, column 4 and row 2.

**Exercise 12**

Repeat the exercises 9-11, but instead of using numbers to reference row, column and height, use `dimnames`

.

Image: Cubo completato” by Masakazu “Matto” Matsumoto from Nagoya, Japan – http://flickr.com/photos/vitroids/1527092739/. Licensed under CC BY 2.0 via Wikimedia Commons.

kd says

Would be nice to have solutions to this exercises as well.

Jon says

Clarification needed for Exercise #7 onwards.

My multi-dimentional array has the dimensions 3*2*4, which I assume corresponds to row*column*height as per E#9. Therefore E#10 and E#11 don’t work, since your number of columns is 2.

Please let me know if I’m misinterpreting this. Thanks!

ted says

I like the structure, exercises, and the solutions for validation. I wish if you have a link for array exercise solution

prashanth says

hello

could you please provide solutions for this exercise. i am stuck with questions 9-12

Kung Fury says

Shared my own solutions in rpubs: http://rpubs.com/onurhan/r-exercises-4-2 . please share your comments!

sergio says

Thanks a lot! very usefull!

Arboc says

Thank you! I checked your answer on exercise no. 5 and I hadn’t found aperm() myself so that really helped 🙂 I think the exercise wants us to transpose from column-major to row-major input for each level of [, , x]. So if the numbers are 1:24, in each “box” of columns and rows, the numbers should be going “1, 2, 3…” row-wise. Like this:

x y z

a 1, 2, 3

b 4, 5, 6

I’m not well versed enough to understand entirely what happens if we call aperm() with the argument perm = NULL, but it looks like the output you got is slightly different from what the exercise asked us to do.

I tried this instead, and it seems to work for exercise 5:

dnam <- list(c('a', 'b', 'c', 'd'), c('A', 'B'), c('D1', 'D2', 'D3'))

rarr2 <- array(1:24, dim = c(4, 2, 3),

dimnames = dnam)

rarr3 <- aperm(rarr2, perm = c(2, 1, 3))

I hope this helps someone!

Plum says

Where are the solutions?