alma(src, len, offset, sigma, _id) {
        let id = this._tsid(_id, `alma(${len},${offset},${sigma})`)
        let m = Math.floor(offset * (len - 1))
        let s = len / sigma
        let norm = 0
        let sum = 0
        for (var i = 0; i < len; i++) {
            let w = Math.exp(-1 * Math.pow(i - m, 2) / (2 * Math.pow(s, 2)))
            norm = norm + w
            sum = sum + src[len - i - 1] * w
        }
        return this.ts(sum / norm, id, src.__tf__)
    }
Arnaud Legoux Moving Average
@param {TS} src - Input
@param {number} len - Length
@param {number} offset - Offset
@param {number} sigma - Sigma
@return {TS} - New time-series