🔧 Use Julian Day as internal date representation (#3)

This commit added compatibility with automatic differentiation packages.

Project.toml

@@ -21,6 +21,10 @@ julia = "1.6"
 [extras]
 Logging = "56ddb016-857b-54e1-b83d-db4d58db5568"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
+ForwardDiff = "f6369f11-7733-5829-9624-2563aa707210"
+ReverseDiff = "37e2e3b7-166d-5795-8a7a-e32c996b4267"
+Zygote = "e88e6eb3-aa80-5325-afca-941959d7151f"
+
 
 [targets]
-test = ["Test", "Logging"]
+test = ["Test", "Logging", "ForwardDiff", "ReverseDiff", "Zygote"]

docs/src/man/api.md

@@ -79,6 +79,7 @@ signature:
 
 ```julia
 SpaceIndices.space_index(::Val{:index}, instant::DateTime; kwargs...) -> Number
+SpaceIndices.space_index(::Val{:index}, jd::Number; kwargs...) -> Number
 ```
 
 where the space `index` for the `instant` will be returned.

src/API.md

@@ -73,6 +73,7 @@ signature:
 
 ```julia
 SpaceIndices.space_index(::Val{:index}, instant::DateTime; kwargs...) -> Number
+SpaceIndices.space_index(::Val{:index}, jd::Number; kwargs...) -> Number
 ```
 
 where the space `index` for the `instant` will be returned.

src/api.jl

@@ -101,16 +101,16 @@ urls
 
 """
     space_index(::Val{:index}, jd::Number; kwargs...) -> Number
-    space_index(::Val{:index}, instant::DateTime; kwargs...) -> Number
+    space_index(::Val{:index}, date::DateTime; kwargs...) -> Number
 
 Get the space `index` for the Julian day `jd` or the `instant`. The latter must be an object
 of type `DateTime`. `kwargs...` can be used to pass additional configuration for the space
 index.
 """
 space_index
 
-function space_index(index::Val, jd::Number)
-    return space_index(index, julian2datetime(jd))
+function space_index(index::Val, date::DateTime)
+    return space_index(index, datetime2julian(date))
 end
 
 """

src/interpolations.jl

@@ -11,21 +11,25 @@
 # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
 """
-    constant_interpolation(knots::Vector{Date}, values::AbstractVector, x::Date) -> eltype(values)
+    constant_interpolation(knots::AbstractVector, values::AbstractVector, x) -> eltype(values)
 
 Perform a constant interpolation at `x` of `values` evaluated at `knots`. The interpolation
 returns `value(knots[k-1])` in which `knots[k-1] <= x < knots[k]`.
 """
-function constant_interpolation(knots::AbstractVector{Tk}, values::AbstractVector, x::Tk) where Tk
+function constant_interpolation(knots::AbstractVector, values::AbstractVector, x)
     # First, we need to verify if `x` is inside the domain.
-    num_knots = length(knots)
     knots_beg = first(knots)
     knots_end = last(knots)
 
     if !(knots_beg <= x <= knots_end)
+
+        x_dt = julian2datetime(x)
+        knots_beg_dt = julian2datetime(knots_beg)
+        knots_end_dt = julian2datetime(knots_end)
+
         throw(ArgumentError("""
-            There is no available data for x = $(x)!
-            The available interval is: x ∈ [$knots_beg, $knots_end]."""
+            There is no available data for x = $(x_dt)!
+            The available interval is: x ∈ [$knots_beg_dt, $knots_end_dt]."""
         ))
     end
 
@@ -37,46 +41,46 @@ function constant_interpolation(knots::AbstractVector{Tk}, values::AbstractVecto
 end
 
 """
-    linear_interpolation(knots::AbstractVector{Tk}, values::AbstractVector{Tv}, x::Tk) where {Tk, Tv}
+    linear_interpolation(knots::AbstractVector, values::AbstractVector, x)
 
 Perform a linear interpolation at `x` of `values` evaluated at `knots`.
 """
-function linear_interpolation(knots::AbstractVector{Tk}, values::AbstractVector{Tv}, x::Tk) where {Tk, Tv}
+function linear_interpolation(knots::AbstractVector, values::AbstractVector, x)
     # First, we need to verify if `x` is inside the domain.
-    num_knots = length(knots)
     knots_beg = first(knots)
     knots_end = last(knots)
 
     if !(knots_beg <= x <= knots_end)
+        x_dt = julian2datetime(x)
+        knots_beg_dt = julian2datetime(knots_beg)
+        knots_end_dt = julian2datetime(knots_end)
+
         throw(ArgumentError("""
-            There is no available data for x = $(x)!
-            The available interval is: x ∈ [$knots_beg -- $knots_end]."""
+            There is no available data for x = $(x_dt)!
+            The available interval is: x ∈ [$knots_beg_dt -- $knots_end_dt]."""
         ))
     end
 
-    # Type of the returned value.
-    T = float(Tv)
-
     # Find the vector index related to the request interval using binary search. We can
     # apply this algorithm because we assume that `knots` are unique and increasing.
     id = _binary_search(knots, x)
 
     # If we are at the knot precisely, just return it.
     if x == knots[id]
-        return Tv(values[id])
+        return values[id]
 
     else
         # Here, we need to perform the interpolation using the adjacent knots.
         x₀ = knots[id]
         x₁ = knots[id + 1]
 
-        y₀ = T(values[id])
-        y₁ = T(values[id + 1])
+        y₀ = values[id]
+        y₁ = values[id + 1]
 
         Δy = y₁ - y₀
         Δx = x₁ - x₀
 
-        y  = y₀ + Δy * T((x - x₀) / Δx)
+        y  = y₀ + Δy * (x - x₀) / Δx
 
         return y
     end
@@ -88,7 +92,7 @@ end
 
 # Perform a interval binary search of `x` in `v`. It means that this function returns `k`
 # such that `v[k] <= x < v[k + 1]`.
-function _binary_search(v::AbstractVector{T}, x::T) where T
+function _binary_search(v::AbstractVector, x)
     num_elements = length(v)
     low  = 1
     high = num_elements