fix breakage of trajctory for discrete systems (#201)

* fix breakage of trajctory for discrete systems

* bump version

Author: Datseris

Project.toml

@@ -1,7 +1,7 @@
 name = "DynamicalSystemsBase"
 uuid = "6e36e845-645a-534a-86f2-f5d4aa5a06b4"
 repo = "https://github.com/JuliaDynamics/DynamicalSystemsBase.jl.git"
-version = "3.7.0"
+version = "3.7.1"
 
 [deps]
 ForwardDiff = "f6369f11-7733-5829-9624-2563aa707210"

src/core/trajectory.jl

@@ -55,7 +55,7 @@ function trajectory_discrete(ds, T;
     data[1] = obtain_state(current_state(ds), accessor)
     for i in 2:L
         step!(ds, Δt)
-        data[i] = SVector{X, ET}(obtain_state(ds, current_state(ds), accessor))
+        data[i] = SVector{X, ET}(obtain_state(ds, current_time(ds), accessor))
         if !successful_step(ds)
             # Diverged trajectory; set final state to remaining set
             # and exit iteration early

test/mtk_integration.jl

@@ -186,4 +186,3 @@ X, tvec = trajectory(ds, 10.0; Δt = 0.1, save_idxs = Any[1, 2, η1])
 
 @test all(abs.(diff(X[:, 1])) .> 1e-8)
 @test all(diff(X[:, 3]) .≈ 0.001)
-

test/runtests.jl

@@ -15,4 +15,5 @@ testfile(file, testname=defaultname(file)) = @testset "$testname" begin; include
     testfile("projected.jl")
     testfile("successful_step.jl")
     testfile("mtk_integration.jl")
+    testfile("trajectory.jl")
 end

test/trajectory.jl

@@ -0,0 +1,21 @@
+using DynamicalSystemsBase
+using Test
+
+@testset "trajectory with `nothing`" begin
+
+    # time-dependent logistic map, so that the `r` parameter increases with time
+    r1 = 3.83
+    r2 = 3.86
+    N = 2000
+    rs = range(r1, r2; length = N)
+
+    function logistic_drifting_rule(u, rs, n)
+        r = rs[n+1] # time is `n`, starting from 0
+        return SVector(r*u[1]*(1 - u[1]))
+    end
+
+    ds = DeterministicIteratedMap(logistic_drifting_rule, [0.5], rs)
+
+    x, t = trajectory(ds, N-1)
+    @test length(x) > 1
+end