--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/+time/Rk4SecondOrderNonlin.m	Thu Sep 17 10:12:50 2015 +0200
@@ -0,0 +1,74 @@
+classdef Rk4SecondOrderNonlin < time.Timestepper
+    properties
+        F
+        k
+        t
+        w
+        m
+
+        D
+        E
+        S
+
+        n
+    end
+
+
+    methods
+        function obj = Rk4SecondOrderNonlin(D, E, S, k, t0, v0, v0t)
+
+            if S == 0
+                S = @(v,t)0;
+            end
+
+            if E == 0
+                E = @(v,t)0;
+            end
+
+            obj.k = k;
+            obj.t = t0;
+            obj.w = [v0; v0t];
+
+            m = length(v0);
+            function wt = F(w,t)
+                v  = w(1:m);
+                vt = w(m+1:end);
+
+                % Def: w = [v; vt]
+                wt(1:m,1) = vt;
+                wt(m+1:2*m,1) = D(v)*v + E(v)*vt + S(v,t);
+
+            end
+
+            obj.F = @F;
+            obj.D = D;
+            obj.E = E;
+            obj.S = S;
+            obj.m = m;
+        end
+
+        function [v,t] = getV(obj)
+            v = obj.w(1:end/2);
+            t = obj.t;
+        end
+
+        function [vt,t] = getVt(obj)
+            vt = obj.w(end/2+1:end);
+            t = obj.t;
+        end
+
+        function obj = step(obj)
+            obj.w = time.rk4.rungekutta_4(obj.w, obj.t, obj.k, obj.F);
+            obj.t = obj.t + obj.k;
+            obj.n = obj.n + 1;
+        end
+    end
+
+
+    methods (Static)
+        function k = getTimeStep(lambda)
+            k = rk4.get_rk4_time_step(lambda);
+        end
+    end
+
+end
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