Octave array functions

Some predefined functions of Octave are dedicated to arrays and allow you to save a lot of time during calculation operations.

I'll give you some practical examples.

Create an array with five elements and assign it to a vector variable.

>> v = [ 1 4 2 6 3 ]
v =
1 4 2 6 3

Here are some array functions in Octave

sum()

Adds the elements in the array

>> sum(v)
ans = 16

Note. It is the algebraic sum of the numerical values in the array $$ 1 + 4 + 2 + 6 + 3 = 16 $$

prod()

Multiply all the elements of the array

>> prod(v)
ans = 144

Note. Calculates the product of the numeric elements in the array $$ 1 \cdot 4 \cdot 2 \cdot 6 \cdot 3 = 144 $$

length()

Find the number of elements in the array.

>> length(v)
ans = 5

Note. The array consists of five elements [ 1 4 2 6 3 ]

mean()

Calculates the arithmetic mean of the numeric elements of the array

>> mean(v)
ans = 3.2000

Note. The arithmetic mean of the elements of the array is equal to the sum of the elements divided by the number of elements in the array $$ \frac{1+4+2+6+3}{5} = \frac{16}{5} = 3.2 $$

max()

Find the maximum value in the elements of the array

>> max(v)
ans = 6

Note. The maximum value in the array [ 1 4 2 6 3 ] is six.

min()

Find the minimum value in the elements of the array

>> min(v)
ans = 1

Note. The minimum value in the array [ 1 4 2 6 3 ] is one.

find()

Finds elements of the array that satisfy a selection criterion.

This function returns the position of the elements in the array and not their value.

>> find(v>2)
ans =
2 4 5

Note. In this case the values greater than 2 in the array [ 1 4 2 6 3 ] are the elements in position 2, 4 and 5 i.e. the second, fourth and fifth element of the array.

sort()

Sort vector elements in ascending order

>> sort(v, 'ascend')
ans =
1 2 3 4 6

or descending order

>> sort(v, 'descend')
ans =
6 4 3 2 1

The second parameter is 'ascend' by default.

So, if you type sort(v) without specifying the second parameter, Octave sorts in ascending order.

>> sort(v)
ans =
1 2 3 4 6

round()

Rounds array elements to the nearest integer to the right or left of each number.

>> v = [ 0.2 -0.4 1.4 1.9 -2.1 ]
v =
0.20000 -0.40000 1.40000 1.90000 -2.10000

>> round(v)
ans =
0 -0 1 2 -2

fix()

Rounds array elements to the nearest integer to zero.

This function round to the right if the number is negative or to the left if the number is positive.

>> v = [ 0.2 -0.4 1.4 1.9 -2.1 ]
v =
0.20000 -0.40000 1.40000 1.90000 -2.10000

>> fix(v)
ans =
0 -0 1 1 -2

floor()

This function rounds array elements to the nearest integer to minus infinity (-∞) i.e. to the left of the number.

>> v = [ 0.2 -0.4 1.4 1.9 -2.1 ]
v =
0.20000 -0.40000 1.40000 1.90000 -2.10000

>> floor(v)
ans =
0 -1 1 1 -3

ceil()

Rounds array elements to the nearest integer to plus infinity (+∞) i.e. to the right of the number.

>> v = [ 0.2 -0.4 1.4 1.9 -2.1 ]
v =
0.20000 -0.40000 1.40000 1.90000 -2.10000

>> ceil(v)
ans =1 -0 2 2 -2