Standard Deviation

[iraj720]

Hi
I found sth on paper which shows we can calculate SD of a dataset from SD's of its subsets :)
e.g : NEW_FUNCTION(SD({1,3}), SD(5), medians) = SD({1,3,5})
and the use case is where we have calculated the SD of 1000 rows of data and want to calculate SD of 1000 + 1 without processing former data
is this implemented in this library cause i didn't see such a thing
if it seems proper let me know to submit the pull request.
Thanks

[montanaflynn]

There's several standard deviation functions:

func StandardDeviation(input Float64Data) (sdev float64, err error) {}
func StandardDeviationPopulation(input Float64Data) (sdev float64, err error) {}
func StandardDeviationSample(input Float64Data) (sdev float64, err error) {}

[iraj720]

but seems that none of them are doing that thing that i have discussed

[montanaflynn]

I see what you mean now, got a link to the paper or more info? What would the new function be called?

Feel free to submit a PR as well!

[iraj720]

just submitted
#79