Function linear

linear(x1: number, y1: number, x2: number, y2: number): ChalkboardFunction
Defines a linear function with two points.
Parameters
- x1: number
  The x-coordinate of the first point
- y1: number
  The y-coordinate of the first point
- x2: number
  The x-coordinate of the second point
- y2: number
  The y-coordinate of the second point
Returns ChalkboardFunction
Example
```
const line = Chalkboard.real.linear(0, 1, 2, 5);
const y = Chalkboard.real.val(line, 3); // Returns 7
```
- Defined in Chalkboard.real.ts:387