# 3. Objects that contain an array

An array is nothing more than a matrix with more than two dimensions. It is basically a series of two-dimensional matrices “on top of each other”; in other words, a matrix is an array with only two dimensions, or only one layer. To build an array, there is a function called… `array()`, and inside that function, you’ll need to use the option `dim` (dimension) to organize the number of rows, columns… and layers. In the following example, we build an array called `long.box` made of 4 rows, 3 columns and 2 layers, and containing the values ranging from 1 to 24:

[code language=”r”]
long.box <- array(1:24, dim=c(4,3,2))
long.box
[/code]

As seen on the picture above, we obtain 2 matrices each containing 12 values arranged in 4 rows and 3 columns. Each matrix or layer of the array is identify by its “layer number” following 2 commas  `, , 1` and  `, , 2`. Logically, the first layer contains data ranging from 1 to 12 and the second layer contains values from 13 to 24.

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