I'm trying to find a compounding period C when given an annual interest rate r and effective annual yield i. I'm working with the following equation:
$i=(1+r/C)^C-1$
I'm having trouble re-writing the equation for compounding period C in terms of r and i. Is there any closed-form solution to an equation like this, or am I best off trying to approximate C using the bisection method or some other root-fining algorithm?