function getRawValueFromStore(list, dimIndex, rawIndex) {
    var val;
    if (dimIndex != null) {
        var chunkSize = list._chunkSize;
        var chunkIndex = Math.floor(rawIndex / chunkSize);
        var chunkOffset = rawIndex % chunkSize;
        var dim = list.dimensions[dimIndex];
        var chunk = list._storage[dim][chunkIndex];
        if (chunk) {
            val = chunk[chunkOffset];
            var ordinalMeta = list._dimensionInfos[dim].ordinalMeta;
            if (ordinalMeta && ordinalMeta.categories.length) {
                val = ordinalMeta.categories[val];
            }
        }
    }
    return val;
}
Get extent of data in one dimension
@param {string} dim
@param {boolean} stack