Round a number based on a ratio in C#

Question

I would like to round a number that is based on ratio of two values.

The ratio will include values that are greater or less than the original value where

ratio = newValue / originalvalue

When newValue > originalValue I can round to the nearest lower factor using:

double NearestLowerFactor(float value, double factor)
{
    return Math.Floor(value / factor) * factor;
}

For example:

• factor = 2
• ratio = 3
• NearestLowerFactor = 2

When newValue < originalValue I wish to round to the nearest reciprocal of the factor.

Therefore, if the factor is 2 I would like to round based on factors of 1/2, that is 1/2, 1/4, 1/8, 1/16, etc.

For example:

• originalValue = 8
• newValue = 3
• ratio = 0.375
• NearestLowerFactor = 0.25 or 1 / 4.

How would I round to the closest lower factor in this case?

Answer 1

Math.Pow(factor, Math.Floor(Math.Log(ratio, factor)))