Hi,
I understand that you want to extrude a 2D domain into a 3D domain. You are trying to extrude only the second face by a height of 10.
Firstly, you can only extrude a particular face of a 3D geometry, not 2D geometry (as mentioned in https://www.mathworks.com/help/pde/ug/pde.discretegeometry.extrude.html#description) . You can first extrude your 2D geometry to 3D by using extrude(g, height) and then extrude 2nd face of the resultant 3D geometry by using (g,2,height).
Also the input of "extrude" can be only of these types: fegeometry, DiscreteGeometry or AnalyticGeometry object (https://www.mathworks.com/help/pde/ug/pde.discretegeometry.extrude.html#mw_eb61fe69-2246-44c8-91d4-b5be3e4cff40). So you may use the function 'geometryFromEdges' to convert it to an Analytical Geometry object( https://www.mathworks.com/help/pde/ug/pde.pdemodel.geometryfromedges.html )
You may refer to the below code and make adjustments in the face number to obtain your desired geometry:
R1 = [3,4,-1,1,1,-1,-.4,-.4,.4,.4]';
C1 = [1,.5,0,.2]';
C1 = [C1;zeros(length(R1)-length(C1),1)];
C2 = C1;
C2(2,1) = -0.5;
geom = [R1,C1,C2];
ns = (char('R1','C1','C2'))';
% Set formula
sf = 'R1 + C1 + C2';
% Create geometry
gd = decsg(geom,sf,ns);
% View geometry
pdegplot(gd,"FaceLabels","on");
xlim([-1.1 1.1]);
axis equal;
model = createpde("thermal","transient");
ge = geometryFromEdges(model,gd);
% 2D -> 3D extrusion
gd1 = extrude(ge,0.5);
figure
pdegplot(gd1,"FaceLabels","on")
% 3D face extrusion
gd2 = extrude(gd1,2,10);
figure
pdegplot(gd2,"FaceLabels","on","FaceAlpha",.5)
Hope this helps!
