[R] Simplify formula for iterative programming

[Stefaan Lhermitte]

Dear Christoph,

Thanks for your help!
I checked it in R and it works if we extend a and b with one element for 
each run. Unfortunately, I actually want to merge two vectors and then 
calculate the H for the merge. It is consequently no addition of 1 
element but an addition of x elements. I did not mention it in my first 
post in order not to make it too complicated.

The second problem that still remains is that I have to keep the 
original values of my original vectors. In the example I gave with sd  
only a calculated value and the new value are needed. The iterative 
process does not the need previously processed values of A anymore. I 
hoped something comaprable was possible for H.

Thanks anyway for your help!

Kind regards,
Stef