--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/+sbp/upwind3.m	Tue Dec 15 16:38:17 2015 +0100
@@ -0,0 +1,32 @@
+function [H, HI, Dp, Dm, e_1, e_m] = upwind3(m,h)
+    Hv = ones(m,1);
+    Hv(1:3) = [3/8; 7/6; 23/24];
+    Hv(m-2:m) = rot90(Hv(1:3),2);
+    Hv = Hv*h;
+    H = spdiag(Hv,0);
+    HI = spdiag(1./Hv,0);
+
+    q_diags   = [-1, 0, 1, 2];
+    q_stencil = [-1/3 -1/2 1 -1/6];
+    Qp = stripeMatrix(q_stencil, q_diags,m);
+
+    Q_U = [
+         -1/24  17/24   -1/6;
+        -13/24   -1/4  23/24;
+          1/12 -11/24 -11/24;
+    ];
+    Qp(1:3,1:3)=Q_U;
+    Qp(m-2:m,m-2:m)=rot90(Q_U,2)'; %%% This is different from standard SBP
+
+    Qm=-Qp';
+
+    e_1=sparse(m,1);
+    e_1(1)=1;
+    e_m=sparse(m,1);
+    e_m(m)=1;
+
+    Dp=HI*(Qp-1/2*e_1*e_1'+1/2*e_m*e_m') ;
+
+    Dm=HI*(Qm-1/2*e_1*e_1'+1/2*e_m*e_m') ;
+end
+