get-rectangle-points.js

/**
 * @param {number} n: 正n角形
 * @param {number} r: 正n角形の中心から頂点への距離
 * @return Array<{x: number, y: number }>: 座標
 */
function getRectanglePoints(n, r) {
    // canvasに書かれる
    const thetaUnit = Math.PI * 2 / n

    const points = []

    for (let i = 0; i < n; i++) {
        points.push(polarToXY(r, thetaUnit * i))
    }

    return points
}

function polarToXY(r, theta) {
    return {
        x: r * Math.round(Math.cos(theta) * 1000) / 1000,
        y: r * Math.round(Math.sin(theta) * 1000) / 1000
    }
}

module.exports = getRectanglePoints

rader.js

function getRaderChartPoints(r, rates) {
    const thetaUnit = Math.PI * 2 / rates.length
    return rates.map((rate, i) => polarToXY(r * rate, thetaUnit * i))
}

function polarToXY(r, theta) {
    return {
        x: r * Math.round(Math.cos(theta) * 1000) / 1000,
        y: r * Math.round(Math.sin(theta) * 1000) / 1000
    }
}

module.exports = getRaderChartPoints