Question

我不知道该如何解决。为什么说运营商未定义，我该如何解决？

我的猜测是它是由于括号[和]而引起的，但是在删除它们时，它表示无法将int转换为double。

public static void main(String[] args)
{
    double value1 = 5.0;
    double[] valuearray = {1,2,3};
    int p = 2;

System.out.print("The L" + p + "-distance between: " + value1 + " and " + valuearray + " = " + getLpDistance(value1, valuearray, p));

  }
public static Double getLpDistance(double value1, double[] valuearray, int p) {
    int d = 1;
    double tmp = 0;
    for (int i = 1; i <= d; i++) {
      tmp += Math.pow(Math.abs(value1 - valuearray), p);
    }
    return Math.pow(tmp, 1.0 / p);
}

Answer 1

您的猜测是正确的：您不能从数组（valuearray）中减去双精度数组（value1）。

要返回valuearray的每个元素的减法，您必须这样做：

for (int i = 1; i <= d; i++) {
  tmp += Math.pow(Math.abs(value1 - valuearray[i]), p);
}

Answer 2

如果只想测量距离，您的代码看起来就很接近了。我在代码中做了一些更改。危险点是当您将p设置为0时，代码将中断。假设您必须将其作为特殊情况处理。

以下代码供您参考。我已添加评论供您参考。

public class LPDistance {

public static void main(String[] args)
{
    double value1 = 5.0;
    double[] valuearray = {1,2,3};
    //when you have to deal with p = 0, you have to add some conditions in your code to deal with that...
    int p = 2;
    System.out.print("The L" + p + "-distance between: " + value1 + " and " + printArray(valuearray) + " = " + getLpDistance(value1, valuearray, p));

  }
private static String printArray(double[] valuearray) {
    //utility function to print an array
    String arrayPrint = "[ ";
    for(int i=0;i<valuearray.length-1;i++)
        arrayPrint+=valuearray[i]+", ";
    arrayPrint+=valuearray[valuearray.length-1]+" ]";
    return arrayPrint;
}
public static Double getLpDistance(double value1, double[] valuearray, int p) {

    //  int d = 1; don't need to set this if you want to go through all the array elements
    double tmp = 0;
    //updated the loop parameters to traverse through the loop
    for (int i = 0; i < valuearray.length; i++) {
      tmp += Math.pow(Math.abs(value1 - valuearray[i]), 2); // if it is distance, power will be always 2
    }
    //if you will pass p=0, below code will fail.
    return Math.pow(tmp, 1.0 / p);
}

}

为什么在插入[]时未定义运算符？

2 个答案: