.

Sheet6/assemble_1D.m

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+function [K,F] = assemble_1D(x,lambda,f)
+N = length(x);
+K = zeros(N);
+F = zeros(N,1);
+
+for i = 1:N-1
+    h = x(i+1)-x(i);
+    xm = (x(i)+x(i+1))/2; %mid point evaluation
+    lam = lambda(xm);
+    Ke = lam/h * [1 -1; -1 1]; %exact P1 stiffness matrix
+    xm = (x(i)+x(i+1))/2;
+    Fe = f(xm)*h/2 * [1;1]; %mid point quadrature for RHS
+    %assembly into global system
+    K(i:i+1,i:i+1) = K(i:i+1,i:i+1) + Ke; 
+    F(i:i+1) = F(i:i+1) + Fe;
+end
+end