V = (S^n)((1 + R*exp(-d*(n-1)))^n)
You could rewrite that as
( S * (1 + R*exp(-d*(n-1))))^n
( S + S*R*exp(-d*(n-1)) )^n
I wrote the equation as I did so that the two components of it would be separated out in an obvious fashion. Namely, the growth factor and the risk factor. You can attempt to simplify it if you wish, but I don't see the point.
So, your parameters S and d are both slowing the growth, just one does it lineary, and the other does it exponentially with time. Also, the influence of "d", and with it R, dies very quickly, and your model goes to S^n for large n, as long as "d" is not zero.
My guess is that you could replace S and d with just one parameter.
You are getting distracted with the equation itself and losing sight of the model it is representing. The intent here is to model two separate factors:
- 1. The risk of systemic failure (brought on by a multitude of possibilities) modeled by S^n
- 2. The growth, modeled by (1+R*exp(-d*(n-1)))^n
If you were to attempt to fit the model to real data, you would only use the equation from #2 above, not from #1, since #1 converts the formula from a long-term predicted growth model to a long-term
expected value model.
If I had any interest in modeling the short-term future value of bitcoin, then I would choose a completely different model more suitable for such things (such as a biased random walk -- though I would not choose to use that model myself for reasons which are way outside the scope of this thread). Again, I think you misunderstand what I am trying to do here, which is to compute a future
expected value.
Let me go back to my lottery example which I used earlier.
If you are holding a lottery ticket in your hand and the lottery pays 1 million BTC, then what is the expected value of that lottery ticket? It depends on how many lottery tickets have been issued. If 100'000 tickets have been issued, the you can compute the expected value to be 10 BTC. That is the
average value of a lottery ticket. 999'999 tickets will be worth 0 BTC, and 1 will be worth 1 million BTC.
Similarly, I'm not exactly trying to predict how much a Bitcoin will be worth in 1 year, or 2.34 years, or whatever. I'm trying to get an idea for the expected value of 1 BTC in my hand today based on
long-term growth rates and risk factors. My model is factoring
risk into the equation and thus it is not predicting the actual value of BTC, but rather first predicting the actual value of BTC based on the growth portion of the equation, and then discounting the value based on risk factors.
The purpose of this is to develop a rational strategy for selling ones bitcoins so as to maximize the value returned.
Another guess is that a simple quadratic polinomial model on a log chart would have all the power of your model.
By all means, fit the actual data and post the results.
Don't take this the wrong way, but once again you are showing that you do not understand what I am attempting to do.
Anyway, I have obviously made a mistake in bringing up this subject here and I will not repeat it again in the future.