向量的运算

向量运算

向量的点乘

a dot b  theta.                   direction
  > 0    0 < theta < 90.        同向
  0      theta = 90                 垂直
  < 0.   90 < theta < 180     反向

class Vector {
    constructor(...components){
        this.components = components
    }
    zero() {
        // 0
        return new Vector(...new Array(this.components.length).fill(0))
    }
    mag() {
        // ||v|| = sqrt(sum(v))
        return Math.hypot(...this.components)
    }
    negative(){
        // v * -1
        return new Vector(...this.mult(-1).components)
    }
    mult(number){
        // v * number
        return new Vector(...this.components.map(component => component * number))
    }
    div(number){
        // v * number
        return new Vector(...this.components.map(component => component / number))
    }
    normalize(){
        // v / ||v||
        return new Vector(...this.div(this.mag()).components)
    }
    add({components}){
        // sum(v1,v2)
        return new Vector(
           ...components.map((component, index) => this.components[index] + component)
        )
    }
    sub({components}){
        // sub(v1,v2)
        return new Vector(
            ...components.map((component, index) => this.components[index] - component)
         )
    }
    dist(v1){
        // ||v2 - v1||
        return this.sub(v1).mag()
    }
    dot({components}){
        // sum(v1 * v2)
        return components.reduce((acc, component, index) => {
            return acc + component * this.components[index]
        },0)
    }
    toDegress(radians){
        // 转角度乘角度除弧度
        return (radians * 180) / Math.PI
    }
    toRadians(degress){
        // 转弧度乘弧度除以角度
        return (degress * Math.PI) / 180
    }
    angleBetween(other){
        // arccos(a dot b / ||a||||b||)
        return this.toDegress(
            Math.acos(
                this.dot(other) / (this.mag() * other.mag())
            )
        )
    }
}

const log = console.log

const one = new Vector(3,-2,7)
const other = new Vector(0,4,-1)

// log(one.dot(other))
log(one.angleBetween(other))

// const one = new Vector(5,0,0)
// const other = new Vector(-1,8,0)

// log(one.dist(other))

// const one = new Vector(2, 3)
// const other = new Vector(2, 1)
// log(one.add(other))
// // Vector { components: [ 4, 4 ] }
// log(one.sub(other))
// // Vector { components: [ 0, 2 ] }
// const v1 = new Vector(12,-5,0)
// log(v1.normalize())
// const v1 = new Vector(5,-4,7)
// log(v1)
// log(v1.negative())
// log(v1.mag())
// log(v1.zero())
// const v2 = v1.mult(2)
// const v3 = v2.div(2)
// log(v2)
// log(v3)