舍入數到特定分辨率

Question

我知道很多的語言有舍入到一個特定小數位數，如使用Python的能力：

>>> print round (123.123, 1) 
    123.1 
>>> print round (123.123, -1) 
    120.0 

但是我們如何四捨五入到這是一個任意分辨率不是的十進制倍數。例如，如果我想圓一個數目到最近的一半或三分之一，因此：

123.123 rounded to nearest half is 123.0. 
456.456 rounded to nearest half is 456.5. 
789.789 rounded to nearest half is 790.0. 

123.123 rounded to nearest third is 123.0. 
456.456 rounded to nearest third is 456.333333333. 
789.789 rounded to nearest third is 789.666666667. 

Answer 1

您可以輪通過簡單的縮放數量，這是一個由分辨率來劃分乘以數量的任意分辨率（或者更容易，只是按照決議進行劃分）。

然後，在將其縮小回來之前，將它四捨五入到最接近的整數。

在Python（這也是一個很好的僞代碼語言），這將是：

def roundPartial (value, resolution): 
    return round (value/resolution) * resolution 

print "Rounding to halves" 
print roundPartial (123.123, 0.5) 
print roundPartial (456.456, 0.5) 
print roundPartial (789.789, 0.5) 

print "Rounding to thirds" 
print roundPartial (123.123, 1.0/3) 
print roundPartial (456.456, 1.0/3) 
print roundPartial (789.789, 1.0/3) 

print "Rounding to tens" 
print roundPartial (123.123, 10) 
print roundPartial (456.456, 10) 
print roundPartial (789.789, 10) 

print "Rounding to hundreds" 
print roundPartial (123.123, 100) 
print roundPartial (456.456, 100) 
print roundPartial (789.789, 100) 

在上面的代碼，它是roundPartial函數提供的功能，它應該是很容易用round函數將它翻譯成任何程序語言。

它的其餘部分，基本上是一個測試工具，輸出：

Rounding to halves 
123.0 
456.5 
790.0 
Rounding to thirds 
123.0 
456.333333333 
789.666666667 
Rounding to tens 
120.0 
460.0 
790.0 
Rounding to hundreds 
100.0 
500.0 
800.0