使用OxyPlot成图，希望能让y轴变成从上至下变大的形式而不是从下到上变大，希望大噶给点建议

        mymodel.Axes.Add(new LinearColorAxis
        {
            Palette = OxyPalettes.Rainbow(100)
        });


        int X = Convert.ToInt32(textBoxX.Text);//长
        int Z = Convert.ToInt32(textBoxZ.Text);//高
        var matrix_L = new DenseMatrix(Z, X);
        var matrix_M = new DenseMatrix(Z, X);
        var matrix_p = new DenseMatrix(Z, X);
        var matrix_vp = new DenseMatrix(Z, X);
        var matrix_vs = new DenseMatrix(Z, X);
        for (int j = 0; j < X; j++)
        {
            for (int i = 0; i < Z; i++)
            {
                if (i<90)
                {
                    matrix_vp[i, j] = 2000;
                    matrix_vs[i, j] = 1200;
                    matrix_p[i, j] = 2000;
                }
                else if(i<120&&j>i-60&&j<260-i)
                {
                    matrix_vp[i, j] = 2000;
                    matrix_vs[i, j] = 1200;
                    matrix_p[i, j] = 2000;
                }
                else
                {
                    matrix_vp[i, j] = 3000;
                    matrix_vs[i, j] = 2000;
                    matrix_p[i, j] = 2500;
                }

                matrix_L[i, j] = Math.Pow(matrix_vs[i, j].Real, 2) * matrix_p[i, j];
                matrix_M[i, j] = (Math.Pow(matrix_vp[i, j].Real, 2) - 2 * Math.Pow(matrix_vs[i, j].Real, 2)) * matrix_p[i, j];
            }
        }

        var matrix_data = matrix_L.Transpose();


        var data = new double[X, Z];
        for (int j = 0; j < Z; j++)
        {
            for (int i = 0; i < X; i++)
            {
                data[i, j] = matrix_data[i, j].Real;
            }
        }


        var heatmapseries = new HeatMapSeries
        {
            X0 = 0,
            X1 = X,
            Y0 = 0,
            Y1 = Z,
            Interpolate = true,
            RenderMethod = HeatMapRenderMethod.Bitmap,
            Data = data

        };
        mymodel.Series.Add(heatmapseries);
        this.plotView1.Model = mymodel;

    }

这是成图的代码，有能给的建议吗？

public void graben_model()
{
    var mymodel = new PlotModel { Title = "地垒模型" };
    //mymodel.Series.Add(new FunctionSeries(Math.Cos, 0, 10, 0.1, "cos(x)"));
    mymodel.Axes.Add(new LinearColorAxis
    {
        Palette = OxyPalettes.Rainbow(100)
    });


    int X = Convert.ToInt32(textBoxX.Text);//长
    int Z = Convert.ToInt32(textBoxZ.Text);//高
    var matrix_L = new DenseMatrix(Z, X);
    var matrix_M = new DenseMatrix(Z, X);
    var matrix_p = new DenseMatrix(Z, X);
    var matrix_vp = new DenseMatrix(Z, X);
    var matrix_vs = new DenseMatrix(Z, X);
    for (int j = 0; j < X; j++)
    {
        for (int i = 0; i < Z; i++)
        {
            if (i<90)
            {
                matrix_vp[i, j] = 2000;
                matrix_vs[i, j] = 1200;
                matrix_p[i, j] = 2000;
            }
            else if(i<120&&j>i-60&&j<260-i)
            {
                matrix_vp[i, j] = 2000;
                matrix_vs[i, j] = 1200;
                matrix_p[i, j] = 2000;
            }
            else
            {
                matrix_vp[i, j] = 3000;
                matrix_vs[i, j] = 2000;
                matrix_p[i, j] = 2500;
            }

            matrix_L[i, j] = Math.Pow(matrix_vs[i, j].Real, 2) * matrix_p[i, j];
            matrix_M[i, j] = (Math.Pow(matrix_vp[i, j].Real, 2) - 2 * Math.Pow(matrix_vs[i, j].Real, 2)) * matrix_p[i, j];
        }
    }

    var matrix_data = matrix_L.Transpose();


    var data             = new double[X, Z];
    var data_Upside_down = new double[X, Z];
    for (int j = 0; j < Z; j++)
    {
        for (int i = 0; i < X; i++)
        {
            data            [i, j] = matrix_data[i, j].Real;
            data_Upside_down[i, j] = 3000 - data[i, j];
        }
    }


    var heatmapseries = new HeatMapSeries
    {
        X0 = 0,
        X1 = X,
        Y0 = 0,
        Y1 = Z,
        Interpolate = true,
        RenderMethod = HeatMapRenderMethod.Bitmap,
        Data = data_Upside_down //data

    };
    mymodel.Series.Add(heatmapseries);
    this.plotView1.Model = mymodel;

}