function addItem(tVal) {
        result.push(onlyTick
            ? tVal
            : {
                formattedLabel: labelFormatter(tVal),
                rawLabel: ordinalScale.getLabel(tVal),
                tickValue: tVal
            }
        );
    }
Convert pixel point to data in axis
@param {Array.<number>} point
@param  {boolean} clamp
@return {number} data