到最近的好号码 [英] round to nearest nice number

问题描述

我正在编写一个应用程序，需要将标签舍入到最近的'nice'数字。我将在下面放一些代码来证明这一点，但我的问题是我使用了一系列其他ifs来找到这个数字，但我不能确定上限，所以这不是一个好的策略。是否有任何已知的算法或资源可以帮助我？

I'm writing an application which requires rounding labels to the nearest 'nice' number. I'll put some code below to demonstrate this, but my issue is that I was using a series of else ifs to find this number but I cannot be sure of the upper limit so this isn't really a good strategy. Are there any known algorithms or resources which could help me?

    if (diff <= 1) {
        roundAmount = 0.2;
    } else if (diff <= 5) {
        roundAmount = 1;
    } else if (diff <= 10) {
        roundAmount = 2;
    } else if (diff <= 25) {
        roundAmount = 5;
    } else if (diff <= 50) {
        roundAmount = 10;
    } else if (diff <= 100) {
        roundAmount = 20;
    } else if (diff <= 250) {
        roundAmount = 50;
    } else if (diff <= 500) {
        roundAmount = 100;
    } else if (diff <= 1000){
        roundAmount = 200;
    } etc...

推荐答案

你可以在进行好数搜索之前，使用 Math.log10 来标准化所有值，如下所示：

You can use Math.log10 to normalize all values before doing your "nice number" search, something like this:

我刚刚意识到你使用的是Java而不是C＃，所以我修改了一下代码。我没有编译器来测试它，但你应该得到一般的想法：

I just realized you are using Java instead of C#, so I modified the code a bit. I don't have a compiler around to test it, but you should get the general idea anyway:

static double getNicerNumber(double val)
{
    // get the first larger power of 10
    var nice = Math.pow(10, Math.ceiling(Math.log10(val)));

    // scale the power to a "nice enough" value
    if (val < 0.25 * nice)
        nice = 0.25 * nice;
    else if (val < 0.5 * nice)
        nice = 0.5 * nice;

    return nice;
}

// test program:
static void main(string[] args)
{
    double[] values = 
    {
        0.1, 0.2, 0.7,
        1, 2, 9,
        25, 58, 99,
        158, 267, 832
    };

    for (var val : values)
        System.out.printf("$%.2f --> $%.2f%n", val, getNicerNumber(val));
}

这将打印如下内容：

0,1 --> 0,1
0,2 --> 0,25
0,7 --> 1
1 --> 1
2 --> 2,5
9 --> 10
25 --> 50
58 --> 100
99 --> 100
158 --> 250
267 --> 500
832 --> 1000

这篇关于到最近的好号码的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！