--- a/+rv/+time/RungekuttaExteriorRV.m	Thu Dec 06 17:03:22 2018 +0100
+++ b/+rv/+time/RungekuttaExteriorRV.m	Fri Dec 07 13:11:53 2018 +0100
@@ -7,16 +7,16 @@
         n       % Time level
         coeffs  % The coefficents used for the RK time integration
         RV      % Residual Viscosity
-        bdfOrder
         v_prev  % Solution vector at previous time levels, used for the RV update
         DvDt    % Function for computing the time deriative used for the RV update
-
-
-        dudt
+        lowerBdfOrder % Orders of the approximation of the time deriative, used for the RV update.
+                      % dictates which accuracy the boot-strapping should start from.
+        upperBdfOrder % Orders of the approximation of the time deriative, used for the RV update.
+                      % Dictates the order of accuracy used once the boot-strapping is complete.
     end
     methods
 
-        function obj = RungekuttaExteriorRV(F, k, t0, v0, RV, rkOrder, bdfOrder, dudt)
+        function obj = RungekuttaExteriorRV(F, k, t0, v0, RV, rkOrder, bdfOrders)
             obj.F = F;
             obj.k = k;
             obj.t = t0;
@@ -28,16 +28,17 @@
             obj.coeffs = struct('s',s,'a',a,'b',b,'c',c);
         
             obj.RV = RV;
-            %  TBD: For cases where h~k we could probably use rkOrder-2 here.
             %  TBD: Decide on if the initialization of the previous stages used by
             %       the BDF should be done here, or if it should be checked for each
             %       step taken.
-            assert((bdfOrder >= 1) && (bdfOrder <= 6));
-            obj.bdfOrder = bdfOrder;
+            %       If it is moved here, then multiple branching stages can be removed in step()
+            %       but this will effectively result in a plotted simulation starting from n = upperBdfOrder.
+            %       In addition, the properties lowerBdfOrder and upperBdfOrder can be removed.
+            obj.lowerBdfOrder = bdfOrders.lowerBdfOrder;
+            obj.upperBdfOrder = bdfOrders.upperBdfOrder;
+            assert((obj.lowerBdfOrder >= 1) && (obj.upperBdfOrder <= 6));
             obj.v_prev = [];
-            obj.DvDt = rv.time.BDFDerivative();
-
-            obj.dudt = dudt;
+            obj.DvDt = rv.time.BdfDerivative();
         end
 
         function [v, t] = getV(obj)
@@ -52,8 +53,10 @@
 
         function obj = step(obj)
             % Store current time level
-            if (size(obj.v_prev,2) < obj.bdfOrder)
+            numStoredStages = size(obj.v_prev,2);
+            if (numStoredStages < obj.upperBdfOrder)
                 obj.v_prev = [obj.v, obj.v_prev];
+                numStoredStages = numStoredStages+1;
             else
                 obj.v_prev(:,2:end) = obj.v_prev(:,1:end-1);
                 obj.v_prev(:,1) = obj.v;
@@ -64,11 +67,10 @@
             obj.t = obj.t + obj.k;
             obj.n = obj.n + 1;
             % Calculate dvdt and update RV for the new time level
-            dvdt = obj.DvDt.evaluate(obj.v, obj.v_prev, obj.k);
-            if ((size(obj.v_prev,2) >= 4) && (size(obj.v_prev,2) <= obj.bdfOrder))
+            if ((numStoredStages >=  obj.lowerBdfOrder) && (numStoredStages <= obj.upperBdfOrder))
+                dvdt = obj.DvDt.evaluate(obj.v, obj.v_prev, obj.k);
                 obj.RV.update(obj.v,dvdt);
             end
-            %obj.RV.update(obj.v,obj.dudt(obj.t));
         end
     end
 end
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