lowestbars(src, len, _id) {
        let id = this._tsid(_id, `lowestbars(${len})`)
        let low = Infinity
        let li = 0
        for (var i = 0; i < len; i++) {
            if (src[i] < low) { low = src[i], li = i }
        }
        return this.ts(-li, id, src.__tf__)
    }
Lowest value offset for a given number of bars back
@param {TS} src - Input
@param {number} len - Length