tr(fixnan = false, _id, _tf) {
        let id = this._tsid(_id, `tr(${fixnan})`)
        let tfs = _tf || ''
        let high = this.env.shared[`high${tfs}`]
        let low = this.env.shared[`low${tfs}`]
        let close = this.env.shared[`close${tfs}`]
        let res = 0
        if (this.na(close[1]) && fixnan) {
            res = high[0] - low[0]
        } else {
            res = Math.max(
                high[0] - low[0],
                Math.abs(high[0] - close[1]),
                Math.abs(low[0] - close[1])
            )
        }

        return this.ts(res, id, _tf)

    }
True Range
@param {TS} fixnan - Fix NaN values
@return {TS} - New time-series