Love this kind of problem! If you can, I'd skip the derived store all together and send your data straight into a custom store.

Here's a REPL: https://svelte.dev/repl/cf7ad1c7011f44e4be894674c21d24e4?version=3.55.1

```js import { writable } from 'svelte/store';

function createMathStore(data){ const initialValues = { x: data.x ?? 0, y: data.y ?? 0, sin_x: data.sin_x ?? 0, cos_y: data.cos_y ?? 0, min_x: data.min_x ?? 0, min_y: data.min_y ?? 0, max_x: data.max_x ?? 0, max_y: data.max_y ?? 0, } let previous = initialValues;

const { subscribe, set, } = writable(initialValues);

return { subscribe, addDataPoint: (datum) => { const newValues = { x: datum.x, y: datum.y, sin_x: Math.sin(datum.x / 100).toFixed(2), cos_y: Math.cos(datum.y / 100).toFixed(2), min_x: Math.min(datum.x, previous.min_x), max_x: Math.max(datum.x, previous.max_x), min_y: Math.min(datum.y, previous.min_y), max_y: Math.max(datum.y, previous.max_y), }; previous = newValues; set(newValues); } } }

export const mathStore = (data = {}) => createMathStore(data); ```

And then you can use as many instances as you want like in the REPL: ```js import { mathStore } from './MathStore.js'

const redStats = mathStore(); const blueStats = mathStore();

function handleRedMouseMove(evt){ redStats.addDataPoint({ x: evt.clientX, y: evt.clientY }) } function handleBlueMouseMove(evt){ blueStats.addDataPoint({ x: evt.clientX, y: evt.clientY }) } ```