How to assign a sparse matrix in Eigen?

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int n = 10000;
VectorXd x(n), b(n);
SparseMatrix<double> A(n,n);

How to assign individual elements of A?
Thanks

it's explained there: http://eigen.tuxfamily.org/dox-devel/Tu ... rseFilling

ggael wrote:it's explained there: http://eigen.tuxfamily.org/dox-devel/Tu ... rseFilling

Unfortunately, I do not understand what it does. Can you give me an example? For instance, how should I assign the following 10 by 8 sparse matrix?

A(1,2) = 3; A(1,4) = 10;
A(2,1) = 9; A(2,8) = 9;
A(4,7) = 11;
A(7,4) = 21;
A(9,3) = 45;
A(10,7) = 76;

You can simply use:

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A.coeffRef(1,2) = 3;
A.coeffRef(1,4) = 10;
...
A.finalize();

But it would be slow, or you can create a a sparse matrix from triplets, such as the example after the "Here is a typical usage example: " in ggael's link.