How do I update my fuel chart from a button?

hello I would like to know how to change my code so that value changes itself without onmouseout or onclick just when I change the value with a button

thank you cordially

Fabien

Here's a demo of updating a Fuel chart with a random value whenever you click the button:

https://codepen.io/rgraph/pen/WNMomYw

The button click event runs the update function which updates the Fuel chart.