View Coefficients

A PDE model stores coefficients in its EquationCoefficients property. Suppose model is the name of your model. Obtain the coefficients:

coeffs = model.EquationCoefficients;

To see the active coefficient assignment for a region, call the findCoefficients function. For example, create a model and view the geometry.

model = createpde();
geometryFromEdges(model,@lshapeg);
pdegplot(model,FaceLabels="on")
ylim([-1.1,1.1])
axis equal

Specify constant coefficients over all the regions in the model.

specifyCoefficients(model,m=0,d=0,c=1,a=0,f=2);

Specify a different f coefficient on each subregion.

specifyCoefficients(model,m=0,d=0,c=1,a=0,f=3,Face=2);
specifyCoefficients(model,m=0,d=0,c=1,a=0,f=4,Face=3);

Change the specification to have nonzero a on region 2.

specifyCoefficients(model,m=0,d=0,c=1,a=1,f=3,Face=2);

View the coefficient assignment for region 2.

coeffs = model.EquationCoefficients;
findCoefficients(coeffs,Face=2)

ans = 
  CoefficientAssignment with properties:

    RegionType: 'face'
      RegionID: 2
             m: 0
             d: 0
             c: 1
             a: 1
             f: 3

This shows the "last assignment wins" characteristic.

View the coefficient assignment for region 1.

findCoefficients(coeffs,Face=1)

ans = 
  CoefficientAssignment with properties:

    RegionType: 'face'
      RegionID: [1 2 3]
             m: 0
             d: 0
             c: 1
             a: 0
             f: 2

The active coefficient assignment for region 1 includes all three regions, though this assignment is no longer active for regions 2 and 3.

Delete Existing Coefficients

To delete all the coefficients in your PDE model, use delete. Suppose model is the name of your model. Remove all coefficients from model.

delete(model.EquationCoefficients)

To delete specific coefficient assignments, delete them from the model.EquationCoefficients.CoefficientAssignments vector.

coefv = model.EquationCoefficients.CoefficientAssignments;
delete(coefv(2))

Change a Coefficient Assignment

To change a coefficient assignment, you need the coefficient handle. To get the coefficient handle:

You can change any property of the coefficient handle. For example,

coefh1.RegionID = [1,3];
coefh1.a = 2;
coefh1.c = @ccoeffun;