如何在 Java 中计算对数？
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How to compute logarithms in Java?
提问by Lemon Juice
Following is the formula
以下是公式
Percentage of Fat = 495 / (1.0324 - 0.19077 x (LOG10(waist - neck)) + 0.15456 x (LOG10(height))) - 450
脂肪百分比 = 495 / (1.0324 - 0.19077 x (LOG10(腰围 - 颈部)) + 0.15456 x (LOG10(height))) - 450
Following is my code
以下是我的代码
import java.math.*;
public class Position
{
static double waist=66,neck=30,height=150;
public static void main(String[]args)
{
double fat = 495 / ( (1.0324 - 0.19077)* (Math.log(waist - neck)/Math.log(10)) + (0.15456) * (Math.log(height)/Math.log(10))) - 450;
System.out.println(fat);
}
}
The answer I get is incorrect. It should be 11.8% (Use the following http://lowcarbdiets.about.com/library/blbodyfatcalculator.htm)
我得到的答案是不正确的。它应该是 11.8%（使用以下http://lowcarbdiets.about.com/library/blbodyfatcalculator.htm）
I believe I have done something incorrectly in logarithms. Please help me to get the correct answer.
我相信我在对数方面做错了一些事情。请帮助我得到正确的答案。
回答by eis
You have written it incorrectly to code. Try with:
您将其错误地编写为代码。尝试：
import java.math.*;
public class Position
{
static double waist=66,neck=30,height=150;
public static void main(String[]args)
{
double fat = 495 / ( 1.0324
- (0.19077 * (Math.log(waist - neck)/Math.log(10)))
+ (0.15456) * (Math.log(height)/Math.log(10))
) - 450;
System.out.println(fat);
}
}
The difference is that this doesn't have 1.0324 - 0.19077- the original formula didn't have it either, so you had misplaced parenthesis.
不同之处在于它没有1.0324 - 0.19077- 原始公式也没有它，所以你放错了括号。
As noted by @a_horse_with_no_name, Math.log() will use e-based logarithm, and not 10-based, but in the scope of this code the result is the same. To use 10-based, you'd use Math.log10().
正如@a_horse_with_no_name 所指出的，Math.log() 将使用基于 e 的对数，而不是基于 10 的对数，但在此代码的范围内，结果是相同的。要使用基于 10 的，您将使用 Math.log10()。
回答by Henry
The log calculation is correct but you have misplaced some parenthesis.
对数计算是正确的，但您放错了一些括号。
double fat = 495 / ( 1.0324 - 0.19077* (Math.log(waist - neck)/Math.log(10)) + (0.15456) * (Math.log(height)/Math.log(10))) - 450
回答by Nikolay Kuznetsov
495 / (1.0324 - 0.19077 x
and this
还有这个
495 / ( (1.0324 - 0.19077)*
does not match
不匹配
