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p5.js mag() Function

Last Updated : 12 Jul, 2025
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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:
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: javascript
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: calculate-mag Online editor: https://editor.p5js.org/ Environment Setup: https://www.geeksforgeeks.org/javascript/p5-js-soundfile-object-installation-and-methods/ Reference: https://p5js.org/reference/#/p5/mag

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