Yesterday for the first time I placed my shiny mareep on the gym and found that she almost does not lose cp. I read the post about cp decay ( https://pokemongo.gamepress.gg/meta-analysis-gym-defense ) and found that there is a gym cp decay formula,
CP_drop/hour = 4.975 * 1.001616 ^ (MaxCP).
Some posts say it only applies for when MaxCP is smaller than 2400, but anyway it seems weird. You know, it's very unlikely Niantic made such a bizarre formula. I kinda like mathematical analysis of games and in the past did much analysis for other games, and this formula doesn't seem intuitive. I think there must be an missing factor that was not considered.
Is there a improved formula for the cp decay?
By the way, by differentiating it I found that about 620 CP is where you can minimize CP lose. My mareep was about 680 CP.
Yes, this function roughly fits the data, but is most certainly not the function used by the programmers. If I look at the data points given by DrThod in the linked article, what they used is an exponential growth function with a floor of 1% CP_drop/hour. I make the exact formula
CP_drop/hour = 1%+0.3%*exp(MaxCP/700) ,
with MaxCP the original CP of the undecayed defender. The limit, at which the 10% cap comes into effect, would in this case be 2381 CP.
