I'm trying to do the maths to calculate the estimate revenue for a given period (day, week, month, year)
So for example, if I have data for 30 days, I need to estimate what would be my income tomorrow.
At the moment what I'm doing is quite simple:
- Calculate growth rate per day for the past 7 days
- Do the average of each of those rates (for example, 20%)
- Now apply that growth rate to the previous day
The problem I'm having is having to deals with days where revenue is 0.
I can't calculate the growth rate for it. The way I'm doing it now is:
growth rate = ((day - previous_day) / previous_day) * 100
So I definitely can't divide by 0 if any previous day has $0 revenue. And it also wouldn't make sense to say my growth rate is 100% is one day it goes from 0 to 1.
What should I do in these cases?
Perhaps ignore those previous days and not taking them to account for the growth rate calculation? Should I also ignore any day which value is also 0?
Right now I'm ignoring it, but then I get things like this:
Array
(
[0] => 0
[1] => 0
[2] => 0
[3] => 259.39
[4] => 259.39 //estimated
)
Which do not look right at all.