aivika-experiment-chart-1.4: examples/DifferenceEquations/Model.hs

{-# LANGUAGE RecursiveDo #-}

module Model (model) where

import Simulation.Aivika
import Simulation.Aivika.SystemDynamics
import Simulation.Aivika.Experiment

model :: Simulation Results
model =
  mdo x <- memoRandomNormalDynamics 3 0.8
      sumX <- diffsum x 0
      sumX2 <- diffsum (x * x) 0
      
      -- it would be much more efficient to say:
      --   let n = fmap fromIntegral integIteration
      n <- diffsum 1 0

      let avg = ifDynamics (n .>. 0) (sumX / n) 0
      let std = ifDynamics (n .>. 1) (sqrt ((sumX2 - sumX * avg) / (n - 1))) 0

      return $
        results
        [resultSource "t" "time" time,
         resultSource "n" "n" n,
         resultSource "x" "x" x,
         resultSource "sumX" "sum x" sumX,
         resultSource "sumX2" "sum x^2" sumX2,
         resultSource "avg" "Ex" avg,
         resultSource "std" "sqrt(Dx)" std]