random-zonotope generation

docs/src/lib/representations.md

@@ -514,6 +514,7 @@ Inherited from [`AbstractSingleton`](@ref):
 Zonotope
 σ(::AbstractVector{Real}, ::Zonotope{Real})
 ∈(::AbstractVector{Real}, ::Zonotope{Real})
+rand(::Type{Zonotope})
 vertices_list(::Zonotope)
 center(::Zonotope)
 order(::Zonotope)

src/Zonotope.jl

@@ -1,4 +1,5 @@
-import Base:∈
+import Base: rand,
+             ∈
 
 export Zonotope,
        order,
@@ -238,6 +239,52 @@ function ∈(x::AbstractVector{N}, Z::Zonotope{N};
     return (lp.status == :Optimal) # Infeasible or Unbounded => false
 end
 
+"""
+    rand(::Type{Zonotope}; [N]::Type{<:Real}=Float64, [dim]::Int=2,
+         [rng]::AbstractRNG=GLOBAL_RNG, [seed]::Union{Int, Nothing}=nothing
+        )::Zonotope{N}
+
+Create a random zonotope.
+
+### Input
+
+- `Zonotope`       -- type for dispatch
+- `N`              -- (optional, default: `Float64`) numeric type
+- `dim`            -- (optional, default: 2) dimension
+- `rng`            -- (optional, default: `GLOBAL_RNG`) random number generator
+- `seed`           -- (optional, default: `nothing`) seed for reseeding
+- `num_generators` -- (optional, default: `-1`) number of generators of the
+                      zonotope (see comment below)
+
+### Output
+
+A random zonotope.
+
+### Algorithm
+
+All numbers are normally distributed with mean 0 and standard deviation 1.
+
+The number of generators can be controlled with the argument `num_generators`.
+For a negative value we choose a random number in the range `dim:2*dim` (except
+if `dim == 1`, in which case we only create a single generator).
+"""
+function rand(::Type{Zonotope};
+              N::Type{<:Real}=Float64,
+              dim::Int=2,
+              rng::AbstractRNG=GLOBAL_RNG,
+              seed::Union{Int, Nothing}=nothing,
+              num_generators::Int=-1
+             )::Zonotope{N}
+    rng = reseed(rng, seed)
+    center = randn(rng, N, dim)
+    if num_generators < 0
+        num_generators = (dim == 1) ? 1 : rand(dim:2*dim)
+    end
+    generators = randn(rng, N, dim, num_generators)
+    return Zonotope(center, generators)
+end
+
+
 # --- Zonotope functions ---
 
 

test/unit_Zonotope.jl

@@ -1,4 +1,7 @@
 for N in [Float64, Rational{Int}, Float32]
+    # random zonotope
+    rand(Zonotope)
+
     # 1D Zonotope
     z = Zonotope(N[0], Matrix{N}(I, 1, 1))
     # Test Dimension