In mathematics, the **dot product** or also known as the **scalar product** is an algebraic operation that takes two equal-length sequences of numbers and returns a single number. Let us given two vectors **A** and **B, **and we have to find the dot product of two vectors.

Given that,

and,

where,

i:the unit vector along the x directions

j:the unit vector along the y directions

k:the unit vector along the z directions

Then the dot product is calculated as:

**Example:**

Given two vectors A and B as,

A = 3i + 5j + 4k,

and

B = 2i + 7j + 5k

Dot Product = 3 * 2 + 5 * 7 + 4 * 5 = 6 + 35 + 20 + 61

#### Computing Dot Product in R

R language provides a very efficient method to calculate the dot product of two vectors. By using **dot()** method which is available in the **geometry** library one can do so.

Syntax:dot(x, y, d = NULL)

Parameters:

x:Matrix of vectors

y:Matrix of vectors

d:Dimension along which to calculate the dot product

Return:Vector with length of dth dimension

**Example 1:**

## R

`# R Program illustrating` `# dot product of two vectors` ` ` `# Import the required library` `library` `(geometry)` ` ` `# Taking two scalar values` `a = 5` `b = 7` ` ` `# Calculating dot product using dot()` `print` `(` `dot` `(a, b, d = ` `TRUE` `))` |

**Output:**

[1] 35

**Example 2:**

## R

`# R Program illustrating` `# dot product of two vectors` ` ` `# Import the required library` `library` `(geometry)` ` ` `# Taking two complex values` `a = 3 + 1i` `b = 7 + 6i` ` ` `# Calculating dot product using dot()` `print` `(` `dot` `(a, b, d = ` `TRUE` `))` |

**Output:**

[1] 15+25i

**Example 3:**

## R

`# R Program illustrating` `# dot product of two vectors` ` ` `# Import the required library` `library` `(geometry)` ` ` `# Taking two simple vectors` `a = ` `c` `(1, 4)` `b = ` `c` `(7, 4)` ` ` `# Calculating dot product using dot()` `print` `(` `dot` `(a, b, d = ` `TRUE` `))` |

**Output:**

[1] 23

**Example 4:**

In this following example let’s take two 2D arrays and calculate the dot product of these two. To create a 2D array in R please refer Multidimensional Array in R.

## R

`# R Program illustrating` `# dot product of two vectors` ` ` `# Import the required library` `library` `(geometry)` ` ` `# Taking two 2D array` `vector1 = ` `c` `(2, 1)` `vector2 = ` `c` `(0, 3)` `a = ` `array` `(` `c` `(vector1, vector2), dim = ` `c` `(2, 2))` `vector1 = ` `c` `(4, 2)` `vector2 = ` `c` `(9, 3)` `b = ` `array` `(` `c` `(vector1, vector2), dim = ` `c` `(2, 2))` ` ` `# Calculating dot product using dot()` `print` `(` `dot` `(a, b, d = ` `TRUE` `))` |

**Output:**

[1] 10 9