Plots.findnz for sparse and non-sparse matrices

src/Plots.jl

@@ -10,7 +10,7 @@ using Reexport
 
 import GeometryTypes
 using Dates, Printf, Statistics, Base64, LinearAlgebra, Random
-import SparseArrays: findnz
+import SparseArrays: AbstractSparseMatrix, findnz
 
 using FFMPEG
 

src/recipes.jl

@@ -1415,7 +1415,7 @@ end
 @recipe function f(::Type{Val{:spy}}, x, y, z)
     yflip := true
     aspect_ratio := 1
-    rs, cs, zs = findnz(z.surf)
+    rs, cs, zs = Plots.findnz(z.surf)
     xlims := ignorenan_extrema(cs)
     ylims := ignorenan_extrema(rs)
     if plotattributes[:markershape] == :none
@@ -1435,6 +1435,18 @@ end
     ()
 end
 
+
+Plots.findnz(A::AbstractSparseMatrix) = findnz(A)
+
+# fallback function for finding non-zero elements of non-sparse matrices
+function Plots.findnz(A::AbstractMatrix)
+    keysnz = findall(!iszero, A)
+    rs = [k[1] for k in keysnz]
+    cs = [k[2] for k in keysnz]
+    zs = A[keysnz]
+    rs, cs, zs
+end
+
 # -------------------------------------------------
 
 "Adds ax+b... straight line over the current plot, without changing the axis limits"