  # Cross Product - coded in a numerical software

In this example, we are going to write a function to find the cross product of two given vectors u and v.

If u = [u1 u2 u3] and v = [v1 v2 v3], we know that the product w is defined as w = [(u2v3 – u3v2) (u3v1 - u1v3) (u1v2 - u2v1)].

We can check the function by taking cross products of unit vectors i = [1 0 0], j = [0 1 0], and k = [0 0 1]

First, we create the function in an m-file as follows:

function w = crossprod(u,v)
% We're assuming that both u and v are 3D vectors.
% Naturally, w = [w(1) w(2) w(3)]
w(1) = u(2)*v(3) - u(3)*v(2);
w(2) = u(3)*v(1) - u(1)*v(3);
w(3) = u(1)*v(2) - u(2)*v(1);

Then, we can call the function from any script, as follows in this example:

% Clear screen, clear previous variables and closes all figures
clc; close all; clear
% Supress empty lines in the output
format compact

% Define unit vectors
i = [1 0 0];
j = [0 1 0];
k = [0 0 1];

% Call the previously created function
w1 = crossprod(i,j)
w2 = crossprod(i,k)

disp('*** compare with results by Matlab ***')
w3 = cross(i,j)
w4 = cross(i,k)

And Matlab displays:

w1 =
0     0     1
w2 =
0    -1     0

*** compare with results by Matlab ***
w3 =
0     0     1
w4 =
0    -1     0
>>

From 'Cross Product' to home

From 'Cross Product' to 'Matlab Examples' 