add geomspace

#252

src/FSharp.Stats/Array.fs

@@ -526,3 +526,17 @@ module ArrayExtension =
                 Seq.linspace(start,stop,Num.Value,includeEndpoint) |> Array.ofSeq
             else 
                 Seq.linspace(start,stop,IncludeEndpoint=includeEndpoint) |> Array.ofSeq
+
+        /// <summary>
+        /// Creates a geometric array of floats with values between a given interval
+        /// </summary>
+        /// <param name="start">start value (is included)</param>
+        /// <param name="stop">end value (by default is included)</param>
+        /// <param name="Num">sets the number of elements in the array. Defaults to 50.</param>
+        /// <param name="IncludeEndpoint">If false, the array does not contain the stop value. Defaults to true.</param>
+        static member geomspace(start:float,stop:float,?Num:int,?IncludeEndpoint:bool) : float array = 
+            let includeEndpoint = defaultArg IncludeEndpoint true
+            let num = defaultArg Num 50
+
+            Seq.geomspace (start, stop ,num, includeEndpoint)
+            |> Array.ofSeq

src/FSharp.Stats/List.fs

@@ -211,3 +211,18 @@ module ListExtension =
                 Seq.linspace(start,stop,Num.Value,includeEndpoint) |> List.ofSeq
             else 
                 Seq.linspace(start,stop,IncludeEndpoint=includeEndpoint) |> List.ofSeq
+
+        /// <summary>
+        /// Creates a geometric list of floats with values between a given interval
+        /// </summary>
+        /// <param name="start">start value (is included)</param>
+        /// <param name="stop">end value (by default is included)</param>
+        /// <param name="Num">sets the number of elements in the list. Defaults to 50.</param>
+        /// <param name="IncludeEndpoint">If false, the list does not contain the stop value. Defaults to true.</param>
+        static member geomspace(start:float,stop:float,?Num:int,?IncludeEndpoint:bool) : float list = 
+            let includeEndpoint = defaultArg IncludeEndpoint true
+            let num = defaultArg Num 50
+
+            Seq.geomspace (start, stop ,num, includeEndpoint)
+            |> List.ofSeq
+

src/FSharp.Stats/Seq.fs

@@ -1240,6 +1240,30 @@ module SeqExtension =
                             ceil dif
                     Seq.init (int num) (fun i -> float i + start)
 
+        /// <summary>
+        /// Creates a geometric seq float with values between a given interval
+        /// </summary>
+        /// <param name="start">start value (is included)</param>
+        /// <param name="stop">end value (by default is included)</param>
+        /// <param name="Num">sets the number of elements in the seq. Defaults to 50.</param>
+        /// <param name="IncludeEndpoint">If false, the seq does not contain the stop value. Defaults to true.</param>
+        static member inline geomspace (start:float, stop:float, ?Num:int, ?IncludeEndpoint:bool) : seq<float> = 
+            if start <= 0. || stop <= 0. then
+                failwith "Geometric space can only take positive values."
+
+            let includeEndpoint = defaultArg IncludeEndpoint true
+            let num = defaultArg Num 50
+
+            let logStart = System.Math.Log start
+            let logStop = System.Math.Log stop
+
+            let logStep =
+                match includeEndpoint with
+                | true -> (logStop - logStart) / (float num - 1.)
+                | false -> (logStop - logStart)  / (float num)
+
+            Seq.init num (fun x -> (System.Math.Exp (logStart + float x * logStep)))
+
 
 //    // ########################################################################
 //    /// A module which implements functional matrix operations.

src/FSharp.Stats/Vector.fs

@@ -424,4 +424,18 @@ module VectorExtension =
                 Seq.linspace(start,stop,Num.Value,includeEndpoint) |> Vector.ofSeq
             else 
                 Seq.linspace(start,stop,IncludeEndpoint=includeEndpoint) |> Vector.ofSeq
+
+        /// <summary>
+        /// Creates a geometric vector of floats with values between a given interval.
+        /// </summary>
+        /// <param name="start">start value (is included)</param>
+        /// <param name="stop">end value (by default is included)</param>
+        /// <param name="Num">sets the number of elements in the vector. Defaults to 50.</param>
+        /// <param name="IncludeEndpoint">If false, the vector does not contain the stop value. Defaults to true.</param>
+        static member geomspace(start:float,stop:float,?Num:int,?IncludeEndpoint:bool) : vector = 
+            let includeEndpoint = defaultArg IncludeEndpoint true
+            let num = defaultArg Num 50
+
+            Seq.geomspace (start, stop ,num, includeEndpoint)
+            |> Vector.ofSeq