Stats matchers

[sksamuel]

list.shouldHaveMean(123.45)
list.shouldHaveStandardDeviation(55.123)
list.shouldHaveVariance(9.4)

[alladywek]

I have a few moments regarding details of implementation:

1. what number types do you want to support?
2. what do you think about using BigDecimal as expected value? It gives more precision result and easier calculations
3. It would be great to have second optional parameter (precision: Int) for these methods where user can specify amount of digits after decimal point:
   list.shouldHaveMean(BigDecimal("0.667"), 3)
list.shouldHaveMean(BigDecimal("0.67"), 2)

Problem with Double is that you can specify only 16-17 digits and other will be lost

fun main() {
  val double = 123456789.01234567890123456789
  println(double)                       //1.2345678901234567E8
  println(BigDecimal(double))           //123456789.01234567165374755859375
  println(BigDecimal(double.toString()))//123456789.01234567
}

[sksamuel]

I think BigDecimal is good yes, but I think we should support doubles too. Obviously there can be precision errors, but we regularly test doubles everywhere else, so I think having both options is the best way. Perhaps with your precision parameter idea.

[alladywek]

yep, I agree that both variants it is good idea, so lets summarize which methods we expect (for methods without explicit precision we can set up precision=5 by default):

Collection<Double>.shouldHaveMean(mean: Double, precision: Int)
Collection<Double>.shouldHaveMean(mean: BigDecimal, precision: Int)
Collection<Double>.shouldHaveMean(mean: Double) 
Collection<Double>.shouldHaveMean(mean: BigDecimal)
DoubleArray.shouldHaveMean(mean: Double, precision: Int)
DoubleArray.shouldHaveMean(mean: BigDecimal, precision: Int)
DoubleArray.shouldHaveMean(mean: Double)
DoubleArray.shouldHaveMean(mean: BigDecimal)

Collection<Double>.shouldHaveStandardDeviation(mean: Double, precision: Int)
Collection<Double>.shouldHaveStandardDeviation(mean: BigDecimal, precision: Int)
Collection<Double>.shouldHaveStandardDeviation(mean: Double)
Collection<Double>.shouldHaveStandardDeviation(mean: BigDecimal)
DoubleArray.shouldHaveStandardDeviation(mean: Double, precision: Int)
DoubleArray.shouldHaveStandardDeviation(mean: BigDecimal, precision: Int)
DoubleArray.shouldHaveStandardDeviation(mean: Double)
DoubleArray.shouldHaveStandardDeviation(mean: BigDecimal)

Collection<Double>.shouldHaveVariance(mean: Double, precision: Int)
Collection<Double>.shouldHaveVariance(mean: BigDecimal, precision: Int)
Collection<Double>.shouldHaveVariance(mean: Double)
Collection<Double>.shouldHaveVariance(mean: BigDecimal)
DoubleArray.shouldHaveVariance(mean: Double, precision: Int)
DoubleArray.shouldHaveVariance(mean: BigDecimal, precision: Int)
DoubleArray.shouldHaveVariance(mean: Double)
DoubleArray.shouldHaveVariance(mean: BigDecimal)

... the same for Int.

support for Long, Float, BigDecimal types could be added in future by requirements.
what do you think?

[sksamuel]

@alladywek are you still planning to work on this ?

[alladywek]

Hi @sksamuel , sorry that I am late to reply, but if it is still actual I can pick up this and finish by end of next week.

[sksamuel]

Please do !

…

On Wed, 4 Sep 2019, 09:42 Abbas Abbasov, ***@***.***> wrote: Hi @sksamuel <https://github.com/sksamuel> , sorry that I am late to reply, but if it is still actual I can pick up this and finish by end of next week. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#851>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAFVSGQR2ATYQK4EK4PAKKDQH7CL5ANCNFSM4H2RWKHA> .

[LeoColman]

Closed as per #989