--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/+sbp/D1Nonequidistant.m	Thu Sep 08 13:28:35 2016 +0200
@@ -0,0 +1,79 @@
+classdef D1Nonequidistant < sbp.OpSet
+    properties
+        D1 % SBP operator approximating first derivative
+        H % Norm matrix
+        HI % H^-1
+        Q % Skew-symmetric matrix
+        e_1 % Left boundary operator
+        e_m % Right boundary operator
+        m % Number of grid points.
+        h % Step size
+        x % grid
+    end
+    
+    methods
+        function obj = D1Nonequidistant(m,L,order,option)
+            
+            default_arg('option','Accurate');
+            % 'Accurate' operators are optimized for accuracy
+            % 'Minimal' operators have the smallest possible boundary
+            % closure
+            
+            switch option
+                
+                case {'Accurate','accurate','A'}
+                    
+                    if order == 4
+                        [obj.D1,obj.H,obj.x,obj.h] = sbp.D1_4th_4BP_2shifts(m,L);
+                    elseif order == 6
+                        [obj.D1,obj.H,obj.x,obj.h] = sbp.D1_6th_6BP_3shifts(m,L);
+                    elseif order == 8
+                        [obj.D1,obj.H,obj.x,obj.h] = sbp.D1_8th_8BP_4shifts(m,L);
+                    elseif order == 10
+                        [obj.D1,obj.H,obj.x,obj.h] = sbp.D1_10th_10BP_5shifts(m,L);
+                    elseif order == 12
+                        [obj.D1,obj.H,obj.x,obj.h] = sbp.D1_12th_12BP_6shifts(m,L);
+                    else
+                        error('Invalid operator order %d.',order);
+                    end
+                    
+                case {'Minimal','minimal','M'}
+                    
+                    if order == 4
+                        [obj.D1,obj.H,obj.x,obj.h] = sbp.D1_minimal_4th_3BP_1shifts(m,L);
+                    elseif order == 6
+                        [obj.D1,obj.H,obj.x,obj.h] = sbp.D1_minimal_6th_5BP_2shifts(m,L);
+                    elseif order == 8
+                        [obj.D1,obj.H,obj.x,obj.h] = sbp.D1_minimal_8th_6BP_2shifts(m,L);
+                    elseif order == 10
+                        [obj.D1,obj.H,obj.x,obj.h] = sbp.D1_minimal_10th_8BP_3shifts(m,L);
+                    elseif order == 12
+                        [obj.D1,obj.H,obj.x,obj.h] = sbp.D1_minimal_12th_10BP_4shifts(m,L);
+                    else
+                        error('Invalid operator order %d.',order);
+                    end
+                    
+            end
+            
+            obj.e_1 = sparse(m,1);
+            obj.e_m = sparse(m,1);
+            obj.e_1(1) = 1;
+            obj.e_m(m) = 1;
+            
+            obj.HI = inv(obj.H);
+            obj.Q = obj.H*obj.D1 - obj.e_m*obj.e_m' + obj.e_0*obj.e_0';
+            
+        end
+    end
+    
+    methods (Static)
+        function lambda = smallestGrid(obj)
+            error('Not implmented')
+        end
+    end
+end
+
+
+
+
+