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mkittimkitti
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Merge pull request #411 from eirikbrandsaas/patch-1
Convenience constructors for constant (nearest-neighbor) interpolation
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‎docs/src/convenience-construction.md‎

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## Convenience notation
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For linear and cubic spline interpolations, `LinearInterpolation` and `CubicSplineInterpolation`
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can be used to create interpolating and extrapolating objects handily:
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For constant, linear, and cubic spline interpolations, `ConstantInterpolation`, `LinearInterpolation`, and `CubicSplineInterpolation`
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can be used to create interpolating and extrapolating objects handily.
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### Motivating Example
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By using the convenience constructor one can simplify expressions. For example, the creation of an interpolation object
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```julia
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extrap_full = extrapolate(scale(interpolate(A, BSpline(Linear())), xs), Line())
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```
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can be written as the more readable
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```julia
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extrap = LinearInterpolation(xs, A, extrapolation_bc = Line())
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```
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by using the convenience constructor.
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### Usage
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```julia
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f(x) = log(x)
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xs = 1:0.2:5
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@test isnan(extrap(5.2))
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```
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Irregular grids are supported as well; note that presently only `LinearInterpolation` supports irregular grids.
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Irregular grids are supported as well; note that presently only `ConstantInterpolation` and `LinearInterpolation` supports irregular grids.
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```julia
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xs = [x^2 for x = 1:0.2:5]
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A = [f(x) for x in xs]

‎src/Interpolations.jl‎

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InPlaceQ,
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Throw,
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ConstantInterpolation,
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LinearInterpolation,
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CubicSplineInterpolation,
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‎src/convenience-constructors.jl‎

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# convenience copnstructors for linear / cubic spline interpolations
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# convenience copnstructors for constant / linear / cubic spline interpolations
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# 1D version
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ConstantInterpolation(range::AbstractRange, vs::AbstractVector; extrapolation_bc = Throw()) =
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extrapolate(scale(interpolate(vs, BSpline(Constant())), range), extrapolation_bc)
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ConstantInterpolation(range::AbstractVector, vs::AbstractVector; extrapolation_bc = Throw()) =
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extrapolate(interpolate((range, ), vs, Gridded(Constant())), extrapolation_bc)
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LinearInterpolation(range::AbstractRange, vs::AbstractVector; extrapolation_bc = Throw()) =
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extrapolate(scale(interpolate(vs, BSpline(Linear())), range), extrapolation_bc)
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LinearInterpolation(range::AbstractVector, vs::AbstractVector; extrapolation_bc = Throw()) =
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extrapolate(scale(interpolate(vs, BSpline(Cubic(bc))), range), extrapolation_bc)
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# multivariate versions
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ConstantInterpolation(ranges::NTuple{N,AbstractRange}, vs::AbstractArray{T,N};
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extrapolation_bc = Throw()) where {N,T} =
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extrapolate(scale(interpolate(vs, BSpline(Constant())), ranges...), extrapolation_bc)
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ConstantInterpolation(ranges::NTuple{N,AbstractVector}, vs::AbstractArray{T,N};
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extrapolation_bc = Throw()) where {N,T} =
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extrapolate(interpolate(ranges, vs, Gridded(Constant())), extrapolation_bc)
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LinearInterpolation(ranges::NTuple{N,AbstractRange}, vs::AbstractArray{T,N};
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extrapolation_bc = Throw()) where {N,T} =
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extrapolate(scale(interpolate(vs, BSpline(Linear())), ranges...), extrapolation_bc)
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"""
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LinearInterpolation
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"""
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etp = ConstantInterpolation(knots, A; extrapolation_bc=Throw())
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A shorthand for `extrapolate(interpolate(knots, A, scheme), extrapolation_bc)`,
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where `scheme` is either `BSpline(Constant())` or `Gridded(Constant())` depending on whether
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`knots` are ranges or vectors.
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"""
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ConstantInterpolation
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"""
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etp = CubicSplineInterpolation(knots, A; bc=Line(OnGrid()), extrapolation_bc=Throw())
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‎test/convenience-constructors.jl‎

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@test_throws BoundsError interp(XMIN - ΔX / 2)
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@test_throws BoundsError interp(XMAX + ΔX / 2)
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end
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@testset "1d-regular-grids-constant" begin
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xs = XMIN:ΔX:XMAX
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f(x) = log(x)
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A = [f(x) for x in xs]
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interp = ConstantInterpolation(xs, A) # using convenience constructor
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interp_full = extrapolate(scale(interpolate(A, BSpline(Constant())), xs), Throw()) # using full constructor
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@test typeof(interp) == typeof(interp_full)
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@test interp(XMIN) ≈ f(XMIN)
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@test interp(XMAX) ≈ f(XMAX)
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@test interp(XMIN + ΔX) ≈ f(XMIN + ΔX)
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@test interp(XMAX - ΔX) ≈ f(XMAX - ΔX)
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@test interp(XMIN + ΔX / 2) ≈ f(XMIN + ΔX / 2) atol=.1
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@test_throws BoundsError interp(XMIN - ΔX / 2)
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@test_throws BoundsError interp(XMAX + ΔX / 2)
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end
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@testset "1d-regular-grids-cubic" begin
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xs = XMIN:ΔX:XMAX
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@test_throws BoundsError interp(xmin - ΔX / 2)
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@test_throws BoundsError interp(xmax + ΔX / 2)
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end
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@testset "1d-irregular-grids-constant" begin
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xs = [x^2 for x in XMIN:ΔX:XMAX]
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xmin = xs[1]
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xmax = xs[XLEN]
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f(x) = log(x)
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A = [f(x) for x in xs]
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interp = ConstantInterpolation(xs, A)
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interp_full = extrapolate(interpolate((xs, ), A, Gridded(Constant())), Throw())
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@test typeof(interp) == typeof(interp_full)
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@test interp(xmin) ≈ f(xmin)
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@test interp(xmax) ≈ f(xmax)
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@test interp(xs[2]) ≈ f(xs[2])
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@test interp(xmin + ΔX / 2) ≈ f(xmin + ΔX / 2) atol=.1
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@test_throws BoundsError interp(xmin - ΔX / 2)
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@test_throws BoundsError interp(xmax + ΔX / 2)
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end
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@testset "1d-handling-extrapolation" begin
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xs = XMIN:ΔX:XMAX
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@test_throws BoundsError interp(XMIN + ΔX / 2,YMIN - ΔY / 2)
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@test_throws BoundsError interp(XMAX + ΔX / 2,YMAX + ΔY / 2)
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end
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@testset "2d-regular-grids-constant" begin
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xs = XMIN:ΔX:XMAX
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ys = YMIN:ΔY:YMAX
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f(x, y) = log(x+y)
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A = [f(x,y) for x in xs, y in ys]
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interp = ConstantInterpolation((xs, ys), A)
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interp_full = extrapolate(scale(interpolate(A, BSpline(Constant())), xs, ys), Throw())
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@test typeof(interp) == typeof(interp_full)
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@test interp(XMIN,YMIN) ≈ f(XMIN,YMIN)
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@test interp(XMIN,YMAX) ≈ f(XMIN,YMAX)
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@test interp(XMAX,YMIN) ≈ f(XMAX,YMIN)
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@test interp(XMAX,YMAX) ≈ f(XMAX,YMAX)
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@test interp(XMIN + ΔX,YMIN) ≈ f(XMIN + ΔX,YMIN)
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@test interp(XMIN,YMIN + ΔY) ≈ f(XMIN,YMIN + ΔY)
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@test interp(XMIN + ΔX,YMIN + ΔY) ≈ f(XMIN + ΔX,YMIN + ΔY)
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@test interp(XMIN + ΔX / 2,YMIN + ΔY / 2) ≈ f(XMIN + ΔX / 2,YMIN + ΔY / 2) atol=.1
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@test_throws BoundsError interp(XMIN - ΔX / 2,YMIN - ΔY / 2)
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@test_throws BoundsError interp(XMIN - ΔX / 2,YMIN + ΔY / 2)
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@test_throws BoundsError interp(XMIN + ΔX / 2,YMIN - ΔY / 2)
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@test_throws BoundsError interp(XMAX + ΔX / 2,YMAX + ΔY / 2)
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end
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@testset "2d-regular-grids-cubic" begin
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xs = XMIN:ΔX:XMAX
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@test_throws BoundsError interp(xmin + ΔX / 2,ymin - ΔY / 2)
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@test_throws BoundsError interp(xmax + ΔX / 2,ymax + ΔY / 2)
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end
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@testset "2d-irregular-grids-constant" begin
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xs = [x^2 for x in XMIN:ΔX:XMAX]
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ys = [y^2 for y in YMIN:ΔY:YMAX]
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xmin = xs[1]
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xmax = xs[XLEN]
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ymin = ys[1]
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ymax = ys[YLEN]
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f(x, y) = log(x+y)
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A = [f(x,y) for x in xs, y in ys]
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interp = ConstantInterpolation((xs, ys), A)
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interp_full = extrapolate(interpolate((xs, ys), A, Gridded(Constant())), Throw())
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@test typeof(interp) == typeof(interp_full)
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@test interp(xmin,ymin) ≈ f(xmin,ymin)
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@test interp(xmin,ymax) ≈ f(xmin,ymax)
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@test interp(xmax,ymin) ≈ f(xmax,ymin)
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@test interp(xmax,ymax) ≈ f(xmax,ymax)
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@test interp(xs[2],ymin) ≈ f(xs[2],ymin)
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@test interp(xmin,ys[2]) ≈ f(xmin,ys[2])
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@test interp(xs[2],ys[2]) ≈ f(xs[2],ys[2])
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@test interp(xmin + ΔX / 2,ymin + ΔY / 2) ≈ f(xmin + ΔX / 2,ymin + ΔY / 2) atol=.1
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@test_throws BoundsError interp(xmin - ΔX / 2,ymin - ΔY / 2)
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@test_throws BoundsError interp(xmin - ΔX / 2,ymin + ΔY / 2)
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@test_throws BoundsError interp(xmin + ΔX / 2,ymin - ΔY / 2)
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@test_throws BoundsError interp(xmax + ΔX / 2,ymax + ΔY / 2)
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end
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@testset "2d-handling-extrapolation" begin
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xs = XMIN:ΔX:XMAX

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