# p5.js | mag() Function

• Last Updated : 25 Mar, 2020

The mag() function in p5.js is used to find the magnitude or length of a vector. As a vector does not have a starting position, the magnitude is calculated from position (0, 0) to (x, y). It is equivalent to using dist(0, 0, x, y).

Syntax:

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`mag( a, b )`

Parameters: This function accept two parameters as mentioned above and described below:

• a: It is a number which denotes the first value, that is the “x” coordinate of the vector.
• b: It is a number which denotes the second value, that is the “y” coordinate of the vector.

Return Value: It returns a number with the magnitude of the vector.

Below examples illustrate the mag() function in p5.js:

Example:

 `function` `setup() {``  ``createCanvas(650, 400);``  ``strokeWeight(5);``  ``rect(0, 0, width, height);``  ``textSize(20);`` ` `  ``text(``"Click on the area below to draw"``          ``+ ``" a line and calculate its "``          ``+ ``"magnitude"``, 20, 30);``}`` ` `function` `mousePressed() {``  ``strokeWeight(1);`` ` `  ``// Draw line to where the``  ``// mouse is clicked``  ``line(0, 0, mouseX, mouseY);`` ` `  ``// Calculate the line magnitude``  ``lineMag = mag(mouseX, mouseY);`` ` `  ``// Draw the magnitude text on``  ``// the end of the line``  ``text(lineMag, mouseX, mouseY);``}`

Output: Online editor: https://editor.p5js.org/

Reference: https://p5js.org/reference/#/p5/mag

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