Add "contradiction index" metric

[stepagrus]

Already we have one metric: difference between "voted for" and "voted against".

It would be interesting to have another metric: "contradiction index".

The calculation formula may be as follows:

difference = abs( voted_for - voted_against )
contradiction_index = ( voted_for + voted_against ) / ( difference == 0 ? 0.1 : difference )

[umputun]

I have added a new field controversy to the Comment struct and controversy sorting key for rest /find.

Now we need UI support for this thing. I think all we need is:

• show the value of controversy somehow (hover on scores?)
• add a new sorting mode "controversial" to "sort by" dropdown

[umputun]

controversy value calculated differently, similar to Reddit's version

func (s *DataStore) controversy(ups, downs int) float64 {

	if downs <= 0 || ups <= 0 {
		return 0
	}

	magnitude := ups + downs
	balance := float64(downs) / float64(ups)
	if ups <= downs {
		balance = float64(ups) / float64(downs)
	}
	return math.Pow(float64(magnitude), balance)
}

[vosi]

https://en.wikipedia.org/wiki/Binomial_proportion_confidence_interval

[vosi]

ааа... присмотрелся, вы и так в ту сторону копнули