unsafe public void Analysis(VPointCollection pts)
        {
            _lines.Clear();
            if (pts == null || pts.Count == 0)
            {
                return;
            }

            //analysis values
            float min = pts.GetMinValue();
            float max = pts.GetMaxValue();

            if (min == max)
            {
                Interval = 1;
            }
            if (Interval == 0)
            {
                Interval = 1;
            }

            if ((min < max && Interval < 0) || (min > max && Interval > 0))
            {
                Interval = -Interval;
            }

            min = GetNearestValue(min, Interval, false);
            max = GetNearestValue(max, Interval, true);

            float        cur             = min;
            List <float> analysis_values = new List <float>();

            while (cur <= max)
            {
                analysis_values.Add(cur);
                cur += Interval;
            }

            float[] x_array, y_array, v_array, analysis_array = null;
            pts.Split(out x_array, out y_array, out v_array);

            float *result = null;

            try
            {
                result = SanJiao(x_array, y_array, v_array, analysis_array, pts.Count, 1, min, Interval, 2);

                if (result == null)
                {
                    return;
                }

                int analysis_value_count = (int)result[0];
                int index = 1;
                if (analysis_value_count <= 0)
                {
                    return;
                }

                for (; index <= analysis_value_count;)
                {
                    int        point_count    = (int)result[index++];
                    float      analysis_value = result[index++];
                    LineString line           = new LineString(analysis_value);

                    for (int i = 0; i < point_count; i++)
                    {
                        float x = result[index++];
                        float y = result[index++];
                        if (y <= Helper.InvalidData)
                        {
                            line.AddPoint(new System.Drawing.PointF(x, y));
                        }
                    }

                    if (line.Points.Count > 0)
                    {
                        line.AddVPoint(line.Points[0]);
                    }

                    _lines.Add(line);
                }
            }
            catch (Exception ex)
            {
            }
            finally
            {
                if (result != null)
                {
                    freecPointer(result);
                }
            }
        }