Index: /issm/trunk-jpl/src/m/contrib/tsantos/integrate_field.m
===================================================================
--- /issm/trunk-jpl/src/m/contrib/tsantos/integrate_field.m	(revision 26228)
+++ /issm/trunk-jpl/src/m/contrib/tsantos/integrate_field.m	(revision 26228)
@@ -0,0 +1,22 @@
+function total=integrate_field(index,x,y,field)
+%INTEGRATE_FIELD: integrate a field over a 2D mesh
+%
+%   Usage:
+%      total=integrate_field(index,x,y,field);
+%
+%   Examples:
+%      volume=integrate_field(md.mesh.elements,md.mesh.x,md.mesh.y,md.geometry.thickness);
+
+% areas of each element
+x1=x(index(:,1)); x2=x(index(:,2)); x3=x(index(:,3));
+y1=y(index(:,1)); y2=y(index(:,2)); y3=y(index(:,3));
+areas=(0.5*((x2-x1).*(y3-y1)-(y2-y1).*(x3-x1)));
+
+% element-wise integration
+v1=index(:,1);	v2=index(:,2);	v3=index(:,3);
+elem_int=areas.*mean(field([v1 v2 v3]),2);
+
+% compute integration
+total=sum(elem_int);
+
+end