How create an identity matrix of size N? I found the DiagonalMatrix class and though it would be useful after calling the setIdentity method but later I just can't multiply it by a scalar and add to a SparseMatrix. What else can I use to achieve this effect?

Thanks.

to add a constant to the diagonal of a sparse matrix have a look at this thread:

viewtopic.php?f=74&t=95552

That code adds the value to the first column of the matrix, or something. I am using a SparseMatrix, not a triangular one.

Then increment the iterator until it.index()==j and add the value. Of course this assume the diagonal entries already exists.

I did this instead

Code: Select all

Eigen::SparseMatrix<btScalar,Eigen::RowMajor> A(kSize, kSize);
   
for (int j=0; j<A.outerSize(); ++j) {
    A.insert(j,j) = timeStep*beta + 1;
}


Thanks for the help.