我的输出和矩阵填充-na​​n而不是0，无法弄清楚为什么

Question

所以这是页面排名的代码，我必须在其中填充矩阵并在其上运行公式。由于某种原因，该函数将一些条目填充为nan，其中应为零。这是引起nan的输入。 7是行数，100是powerIterations。网站是往返于google.com到gmail.com。

7 100

google.com gmail.com

google.com maps.com

facebook.com ufl.edu

ufl.edu google.com

ufl.edu gmail.com

maps.com facebook.com

maps.com quora.com

这与quora.com页面没有任何传出页面有关，因此它应该全部返回零等级，而不是nan。

void AdjacencyListorMatrix::PopulateMatrix() {
set<string>::iterator it;
int i;

for (i = 1, it = pages.begin(); it != pages.end(); ++it, i++) {
    vertexMaps[*it] = i;
}

vertices = pages.size();
matrix = new double*[vertices];

for (int i = 0; i < vertices; i++) {
    matrix[i] = new double[vertices];
}

for (int i = 0; i < vertices; i++) {
    for (int j = 0; j < vertices; j++) {
        matrix[i][j] = 0.0;
    }
}

multimap<string, string>::iterator mapIt;

for (mapIt = inputMaps.begin(); mapIt != inputMaps.end(); mapIt++) {
    matrix[vertexMaps[mapIt->second] - 1][vertexMaps[mapIt->first] -1] = 1;
}

int columnAdds[vertices];

for (int i = 0; i < vertices; i++) {
    columnAdds[i] = 0.0;
}

for (int i = 0; i < vertices; i++) {
    for (int j = 0; j < vertices; j++) {
        columnAdds[j] += matrix[i][j];
    }
}

for (int i = 0; i < vertices; i++) {
    for (int j = 0; j < vertices; j++) {
        matrix[i][j] /= columnAdds[j];
    }
}

result = new double[vertices];

for (int i = 0; i < vertices; i++) {
    result[i] = 1.0 / (double) vertices;
}
}

这是课程信息：

class AdjacencyListorMatrix {
private:
    set<string> pages;
    multimap<string, string> inputMaps;
    map<string, long> vertexMaps;
    double **matrix;
    double *result;
    int vertices;

public:
    void PopulateVertices(string from, string to);
    void PopulateMatrix();
    void PageRank(int n);
    ~AdjacencyListorMatrix();
};

     1    2    3    4    5    6 
1    0  nan    0  0.5  nan    0 
2    0  nan  0.5    0  nan  0.5 
3    0  nan    0    0  nan  0.5 
4    0  nan  0.5    0  nan    0 
5    0  nan    0  0.5  nan    0 
6    1  nan    0    0  nan    0 

我如何使这些nan为0？