Use previous value to calculate next value
I'm trying to perform a calculation that is very easy to do in Excel, but I can't find a way to do in RapidMiner. I expected this to be a little tricky in RM, but also thought this would be a common question on the forum. I'm still new to RM, so it's very possible that I have overlooked something.
Basically I need the previous value of an attribute to calculate the next.
Here's an example of a similar calculation in Excel. To calculate B2:
B2 = (B1*2 + A2) / 10
To calculate B3:
B3 = (B2*2 + A3) / 10
And so on. So I'm using the current value of A, and the previous value of B to get the value of B.
OK. I tried the lag operator, but it can't deliver the previous value of 'itself'. Do I need to use a loop operator? If someone could help me with an example I'd be very happy.