java - 诊断 NaN 的原因

Question

我想按列对 2D 数组求和并求平均值，如果 e[i][j] 的值大于 0 ，计数并求和。但我不知道输出是 NaN ,我该如何解决这个问题？

public class d_2DArray {

    public static void main(String [] args){



      double[][] e=   {{0.0,0.0,0.0,0.0},
                        {0.0,0.6,0.0,0.0},
                        {0.0,0.2,0.5,0.1},
                        {0.0,0.2,0.5,0.4},
                        {0.0,0.2,0.5,0.7},
                        {0.0,0.0,0.0,0.9}};



        double[] avg= new double[4];  
        double[] sum= new double[4];
        int i,j,k=0;
        int[][] x=new int [6][4] ;

            //average of column  


        for(j=1;j<e[1].length;j++){   


            sum[j]=0.0;

             for( i= 1; i < e.length; i++)

            if(x[i][j]==1){
                sum[j] +=e[i][j];
                k++;
        }
        avg[j]= sum[j]/k ; 

          System.out.println("Average j="+avg[j]);  

        }



    }
}

Answer 1

此处 k 的值在程序结束时仍为 0，因此将 0 除以 0 得到 NaN。