Add geometric mean primitive

src/Data/Quantity/Math.purs

@@ -38,6 +38,7 @@ module Data.Quantity.Math
   , min2
   , min
   , mean
+  , geomean
   , modulo
   , round
   , gamma
@@ -55,8 +56,8 @@ import Data.Foldable (foldM)
 import Data.Decimal (Decimal)
 import Data.Either (Either)
 import Data.Quantity (Quantity, ConversionError, derivedUnit, asValueIn',
-                      scalar', quantity', toScalar', (⊘), (⊕), (.*))
-
+                      scalar', quantity', toScalar', (⊗), (⊘), (⊕), (.*), pow)
+import Data.Int (toNumber)
 type Result = Either ConversionError Quantity
 
 lift ∷ (Decimal → Decimal) → Quantity → Result
@@ -178,6 +179,11 @@ mean xs = (_ ⊘ n) <$> foldM (⊕) (head xs) (tail xs)
   where
     n = scalar' (Decimal.fromInt (length xs))
 
+geomean ∷ NonEmptyList Quantity → Result
+geomean xs = (_ `pow` (Decimal.fromInt 1 / n)) <$> foldM (⊗) (head xs) (tail xs)
+  where
+    n = Decimal.fromInt (length xs)
+
 modulo ∷ Quantity → Quantity → Result
 modulo = lift2 Decimal.modulo
 

src/Quantities.purs

@@ -26,7 +26,7 @@ import Data.Quantity (ConversionError(..), Quantity, abs, approximatelyEqual, as
                       sqrt, toScalar, toScalar', toStandard, (.*), (⊕), (⊖), (⊗), (⊘)) as DQ
 import Data.Quantity.Math (acos, acosh, acot, acoth, acsc, acsch, asec, asech, asin, asinh, atan,
                            atan2, atanh, ceil, cos, cosh, cot, coth, csc, csch, e, exp, factorial,
-                           floor, gamma, ln, log10, max, max2, mean, min, min2, modulo, pi, round,
+                           floor, gamma, ln, log10, max, max2, mean, geomean, min, min2, modulo, pi, round,
                            sec, sech, sin, sinh, tan, tanh, tau, phi) as DQM
 import Data.Quantity.Physics (avogadroConstant, electronCharge, electronMass, g0,
                               gravitationalConstant, kB, planckConstant, protonMass,

test/Main.purs

@@ -36,7 +36,7 @@ import Data.Quantity (Quantity, (.*), prettyPrint, (⊕), (⊖), (⊗), (⊘),
                       errorMessage, showResult, qNegate, isFinite,
                       ConversionError(..))
 import Data.Quantity as Q
-import Data.Quantity.Math (sin, asin, pi, modulo, max, min, mean, atan2)
+import Data.Quantity.Math (sin, asin, pi, modulo, max, min, mean, geomean, atan2)
 
 import Effect (Effect)
 
@@ -511,6 +511,7 @@ main = runTest do
                            :  (-1.0 .* inch)
                            :   Nil
     let qs3 = NonEmptyList $ (4.2 .* second) :| Nil
+    let qs4 = NonEmptyList $ scalar (3.0) :| scalar 4.0 : scalar 2.0 : Nil
 
     test "max" do
       equal (Right $ scalar 4.0) (max qs1)
@@ -526,7 +527,11 @@ main = runTest do
       equal (Right $ scalar 1.0) (mean qs1)
       equal (Right $ 1.0 .* meter) (mean qs2)
       equal (Right $ 4.2 .* second) (mean qs3)
+    test "geomean" do
 
+
+      equal (Right $ 4.2 .* second) (geomean qs3)
+      equal (Right $ scalar 2.9) (geomean qs4)
   suite "Consistency checks" do
     test "Data.Units.SI.Derived" do
       -- See: https://en.wikipedia.org/wiki/International_System_of_Units#Derived_units