Trifle::Stats / Transponders / Standard Deviation
Learn how to add standard deviation to your series.

Standard Deviation

Standard Deviation transponder expects three variables to be present. It utilises rapid Standard Deviation formula that depends on count, sum of values and sum of square root of values. The easiest way to populate this is to make sure every time you preserve a value, you do something like this.

def duration(value:)
    count: 1,
    sum: value,
    square: value**2

These will make sure your sums are incremented correctly and you can use them to calculate Standard Deviation.

Note: count, sum and square are default values of the keys. You need to pass only overrides.

series = Trifle::Stats.series(...)
=> #<Trifle::Stats::Series:0x0000ffffa14256e8 @series={:at=>[2024-03-22 19:38:00 +0000, 2024-03-22 19:39:00 +0000], :values=>[{events: {count: 42, sum: 2184}}, {events: {count: 33, sum: 1553}}]}>
series.transpond.standard_deviation(path: 'events')
=> #<Trifle::Stats::Series:0x0000ffffa14256e8 @series={:at=>[2024-03-22 19:38:00 +0000, 2024-03-22 19:39:00 +0000], :values=>[{events: {count: 42, sum: 2184, sd: 123}}, {events: {count: 33, sum: 1553, sd: 456}}]}>

Note: path is a list of keys joined by dot. Ie orders.shipped.count would represent value at {orders: { shipped: { count: ... } } }.