Why is polyarea is giving the wrong area for certain polygons?
MATLAB: Is polyarea giving incorrect results
MATLABpolyareapolygons
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The Solver is misclassifying thermal conductivity as global assignment with k1=@(location,~) 1*location.x;. This is happening because at location.x = 0, which is the query point used to detect difference in conductivity, both k1 and k2 yield the same value of zero.
In the meantime a workaround is to add a small noise, like k2=@(location,~) 20*location.x + eps, this should give the correct results.
The code with the workaround looks like the following:
%% set geometry up and solve
model = createpde('thermal','steadystate');
R1=[3 4 0 1 1 0 0 0 1 1]';
R2=[3 4 0.5 1 1 0.5 0.5 0.5 1 1]';
gm=[R1,R2];
sf='R1+R2';
ns=char('R1','R2')
ns=ns';
g=decsg(gm,sf,ns);
figure(1)
pdegplot(g,'FaceLabels','on','EdgeLabels','on')
%% create mesh geometryFromEdges(model,g) generateMesh(model,'Hmax',0.025); figure(2) pdemesh(model);
%% set boundary conditions temperatureTop=@(location,~) 1*location.x thermalBC(model,'Edge',[1],'Temperature',0); thermalBC(model,'Edge',[7:8],'Temperature',temperatureTop); thermalBC(model,'Edge',[2],'HeatFlux',0); thermalBC(model,'Edge',[5:6],'HeatFlux',0);
%Here you can find the function handles for the ThermalConductivity k1=@(location,~) 1*location.x; k2=@(location,~) 20*location.x+eps; %here you see the fix with 'eps'
thermalProperties(model,'Face',2,'ThermalConductivity',k2); thermalProperties(model,'Face',1,'ThermalConductivity',k1);
%% solve model result = solve(model); temp = result.Temperature;
[qx,qy] = result.evaluateHeatFlux;
figure(3) pdeplot(model,'XYData',temp,'Contour','on'); set(gca,'box','on')
This is the resulting plot:
Our development team is currently working on a fix for a future release. It seems to be that this will be fixed in one of the next releases after R2019a.
You can use the "yyaxis" and "ylim" commands to set the y-limit for both axes:
>> figure
>> yyaxis left
>> plot(1:10);
>> yyaxis right
>> plot(2:2:20);
>>
>> f = gcf;
>> yyaxis left
>> ylim(f.Children, [0 5]);
>> yyaxis right
>> ylim(f.Children, [5 10]);
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