StandardDeviationUnion

[iraj720]

hi
we have talked about this in this issue : #78
if we run it we can see that the new algorithm is faster and its clear
because it is working without former data
i also added the usage and benchmarks in the end of examples/main.go which shows its working correct
later i will add the mathematical proof
Thanks

[montanaflynn]

Thanks! Is there anywhere I can read more about this technique, is it usually referred to as Standard Deviation Union? I didn't find anything when searching for that.

We don't need to add timing logs in the example log, but will need to add some tests.

[iraj720]

honestly im facing this problem in real project because we need to calculate SD in absence of former data
and i didnt find such a thing and also such a name
so i just named it by myself and also will upload the proof
we can change its name if its not proper
do you need the mathematical proof before merging it?

[iraj720]

@montanaflynn could you please take a look i think it would be useful to merge it
Thanks