Add plot recipe for Interpolation object (#35)

* add plot recipe for Interpolation object

* avoid for loop

* format

* allow plotting interpolation in 1D

examples/interpolation_2d_Riesz_kernel.jl

@@ -22,8 +22,5 @@ many_nodes = homogeneous_hypercube(N; dim = 2)
 p1 = plot(many_nodes, itp)
 plot!(p1, many_nodes, f, st = :surface)
 
-x = unique(values_along_dim(many_nodes, 1))
-y = unique(values_along_dim(many_nodes, 2))
-z = reshape(itp.(many_nodes), (N, N))
-p2 = plot(x, y, z, linetype = :contourf)
+p2 = plot(itp, st = :contourf)
 plot(p1, p2, layout = (2, 1))

examples/interpolation_2d_polynomials.jl

@@ -22,8 +22,5 @@ many_nodes = homogeneous_hypercube(N; dim = 2)
 p1 = plot(many_nodes, itp)
 plot!(p1, many_nodes, f, st = :surface)
 
-x = unique(values_along_dim(many_nodes, 1))
-y = unique(values_along_dim(many_nodes, 2))
-z = reshape(itp.(many_nodes), (N, N))
-p2 = plot(x, y, z, linetype = :contourf)
+p2 = plot(itp, st = :heatmap)
 plot(p1, p2, layout = (2, 1))

src/visualization.jl

@@ -124,6 +124,24 @@ end
     end
 end
 
+@recipe function f(itp::Interpolation; x_min = 0.0, x_max = 1.0, N = 50)
+    if dim(itp) == 1
+        x = LinRange(x_min, x_max, N)
+        x, itp.(x)
+    elseif dim(itp) == 2
+        nodeset = homogeneous_hypercube(N, x_min, x_max; dim = 2)
+        x = unique(values_along_dim(nodeset, 1))
+        y = unique(values_along_dim(nodeset, 2))
+        z = reshape(itp.(nodeset), (N, N))'
+        xguide --> "x"
+        yguide --> "y"
+        seriestype --> :heatmap # :contourf
+        x, y, z
+    else
+        @error("Plotting an interpolation is only supported for dimension up to 2, but the interpolation has dimension $(dim(itp))")
+    end
+end
+
 @recipe function f(nodeset::NodeSet, vals::AbstractVector)
     if dim(nodeset) == 1
         @series begin

test/test_unit.jl

@@ -611,6 +611,7 @@ using Plots
                 itp = interpolate(nodes, ff)
                 nodes_fine = homogeneous_hypercube(10; dim = dim)
                 @test_nowarn plot(nodes_fine, itp)
+                @test_nowarn plot(itp)
                 if dim == 2
                     # Test if 2D nodes can be plotted into 3D plot
                     nodes2d = homogeneous_hypercube(5; dim = 2)