C# log base 10 and rounding up to nearest power of 10?

if i have a number between 100 and 1000 i want to get the value 3 because 10^3 = 1000. Likewise, if i had a number between 10 and 100 i would want to get the value 2, because 10^2 is 100.

Incase you're wondering, its to do with calculating a probability and i always need to divide through by 10^value, to keep the probability between 0 a开发者_如何学JAVAnd 1. For example if i calculate 9256, i need to divide through by 10^4, so that i get a probability of 0.92

I'm not sure how to do the rounding up and how to do the base 10, could someone please help?

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Math.Ceiling(Math.Log10(x))

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Why can't you just take the log of the number and then round it up? Log 9256 will give you 3.966, round it up to 4 (add one and integerize it if you want), then divide by 10 to the power of 4... you practically answered the question yourself.

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Using the logarithm will work, but you'll also need to consider the rest of the calculation. Dividing out the powers of 10 may be simpler for you:

double Scale(double x)
{
    if(x <= 0} { return 0; }

    while(x > 1.0)
    {
        x /= 10.0;
    }

    return x;
}