View Initial Conditions

A PDE model stores initial conditions in its InitialConditions property. Suppose model is the name of your model. Obtain the initial conditions:

inits = model.InitialConditions;

To see the active initial conditions assignment for a region, call the findInitialConditions 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 initial conditions over all the regions in the model.

setInitialConditions(model,2);

Specify a different initial condition on each subregion.

setInitialConditions(model,3,Face=2);
setInitialConditions(model,4,Face=3);

View the initial condition assignment for region 2.

ics = model.InitialConditions;
findInitialConditions(ics,Face=2)

ans = 
  GeometricInitialConditions with properties:

           RegionType: 'face'
             RegionID: 2
         InitialValue: 3
    InitialDerivative: []

This shows the "last assignment wins" characteristic.

View the initial conditions assignment for region 1.

findInitialConditions(ics,Face=1)

ans = 
  GeometricInitialConditions with properties:

           RegionType: 'face'
             RegionID: [1 2 3]
         InitialValue: 2
    InitialDerivative: []

The active initial conditions assignment for region 1 includes all three regions, though this assignment is no longer active for regions 2 and 3.

Delete Existing Initial Conditions

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

delete(model.InitialConditions)

To delete specific initial conditions assignments, delete them from the model.InitialConditions.InitialConditionAssignments vector.

icv = model.InitialConditions.InitialConditionAssignments;
delete(icv(2))

Change an Initial Conditions Assignment

To change an initial conditions assignment, you need the initial conditions handle. To get the initial condition handle:

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

ics1.RegionID = [1,3];
ics1.InitialValue = 2;
ics1.InitialDerivative = @ut0fun;