特征矩阵取矩阵的每一行的平均值（计算列向量的质心） [英] Eigen class to take mean of each row of matrix (compute Centroid of the column vectors)

问题描述

我真的是C ++的新手，但这就是我想要做的。我有一个4 x 3矩阵：

I am really new with C++ but here is what I am trying to do. I have a 4 by 3 matrix:

100 109.523 119.096
100 89.7169  76.256
100 96.0822 103.246
100 101.084 85.0639

我想计算每行的平均值并将其存储在向量。我正在使用本征库。我想不出任何有效的方法。到目前为止，这是我的代码：

I want to take calculate the mean of each row and store it in some vector. I am using the Eigen library. I cannot think of anything to do this efficiently. Here is my code thus far:

MatrixXd SS(N,n+1);
    MatrixXd Z = generateGaussianNoise(N,n);
    for(int i = 0; i < N; i++){
        SS(i,0) = S0;
        for(int j = 1; j <= n; j++){
                SS(i,j) = SS(i,j-1)*exp((double) (r - pow(sigma,2.0))*dt + sigma*sqrt(dt)*(double)Z(i,j-1));
        }
    }

    cout << SS << endl;
    cout << endl;
    VectorXd S_A(3);
    S_A = SS.row(1);

所以我拥有的是4 x 3矩阵 SS ，现在我想取每一行的均值并将其存储在向量 S_A 中。我对此有很多困难，因此任何建议将不胜感激。

So what I have is a 4 by 3 matrix SS and now I want to take the mean of each row and store it in the vector S_A. I having a lot of difficulty with this, so any suggestions would be greatly appreciated.

推荐答案

您要部分减少：

Vector3d S_A = SS.rowwise().mean();

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