Function linearMap

libs/echarts/echarts.simple.js:18862–18905

* Linear mapping a value from domain to range * @memberOf module:echarts/util/number * @param {(number|Array. )} val * @param {Array. } domain Domain extent domain[0] can be bigger than domain[1] * @param {Array. } range Range extent range[0] can be bigger than range[1]

(val, domain, range, clamp)

 * @return {(number|Array.<number>}
 */
function linearMap(val, domain, range, clamp) {
    var subDomain = domain[1] - domain[0];
    var subRange = range[1] - range[0];

    if (subDomain === 0) {
        return subRange === 0
            ? range[0]
            : (range[0] + range[1]) / 2;
    }

    // Avoid accuracy problem in edge, such as
    // 146.39 - 62.83 === 83.55999999999999.
    // See echarts/test/ut/spec/util/number.js#linearMap#accuracyError
    // It is a little verbose for efficiency considering this method
    // is a hotspot.
    if (clamp) {
        if (subDomain > 0) {
            if (val <= domain[0]) {
                return range[0];
            }
            else if (val >= domain[1]) {
                return range[1];
            }
        }
        else {
            if (val >= domain[0]) {
                return range[0];
            }
            else if (val <= domain[1]) {
                return range[1];
            }
        }
    }
    else {
        if (val === domain[0]) {
            return range[0];
        }
        if (val === domain[1]) {
            return range[1];
        }
    }

    return (val - domain[0]) / subDomain * subRange + range[0];
}

/**
 * Convert a percent string to absolute number.