/// <summary>
/// 传入poiid列表，返回由poiid，经纬度坐标组成的PointList，用于Optics聚类
/// </summary>
/// <param name="items">List（poiid）</param>
/// <returns></returns>
public PointsList create_points(List <string> items)
{
PointsList points = new PointsList();
foreach (var item in items)
{
double[] pointVector = new double[2];
//传入坐标点的经纬度
pointVector[0] = POIcategory[item].Item1;
pointVector[1] = POIcategory[item].Item2;
//添加点到队列（poiid,[longitude latitude]）
points.AddPoint(item, pointVector);
}
return(points);
}
