refactor: 🔥 move derivative function to ootk

src/utils/functions.ts

@@ -1,7 +1,7 @@
 /* eslint-disable require-jsdoc */
 import { AngularDiameterMethod } from '../enums/AngularDiameterMethod';
 import { AngularDistanceMethod } from '../enums/AngularDistanceMethod';
-import { DifferentiableFunction, EcfVec3, Kilometers, Radians, SpaceObjectType } from '../types/types';
+import { EcfVec3, Kilometers, Radians, SpaceObjectType } from '../types/types';
 import { angularVelocityOfEarth, cKmPerSec } from './constants';
 
 /**
@@ -299,26 +299,6 @@ export function covariance(a: number[], b: number[], isSample = false): number {
   return result / (n - m);
 }
 
-/**
- * Calculates the derivative of a differentiable function.
- * @param f The differentiable function.
- * @param h The step size for numerical differentiation. Default value is 1e-3.
- * @returns The derivative function.
- */
-export function derivative(f: DifferentiableFunction, h = 1e-3): DifferentiableFunction {
-  /**
-   * @param x The value at which to calculate the derivative.
-   * @returns The derivative of the function at the given value.
-   */
-  function df(x: number): number {
-    const hh = h * 0.5;
-
-    return (f(x + hh) - f(x - hh)) / h;
-  }
-
-  return df;
-}
-
 /**
  * Calculates the gamma function of a number.
  * @param n - The input number.

test/utils/functions.test.ts

@@ -12,7 +12,6 @@ import {
   createVec,
   csch,
   deg2rad,
-  derivative,
   gamma,
   linearInterpolate,
   log10,
@@ -103,11 +102,6 @@ describe('functions', () => {
     expect(gamma(1)).toMatchSnapshot();
   });
 
-  // derivative
-  it('should be calculate derivative', () => {
-    expect(derivative((x: number) => x * x, 1)).toMatchSnapshot();
-  });
-
   // covariance
   it('should be calculate covariance', () => {
     expect(covariance([1, 2, 3], [1, 2, 3])).toMatchSnapshot();