I have elements in a MatrixXd that I need to access some elements in very non-sequential order. As it stands, I pass in the full matrix along with a vector of the integer indices I'm interested in and have the function step through those integers, like so:

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void f( Eigen::MatrixXd& m, Eigen::VectorXi& idxlist){
 for (unsigned int i=0; i!=idxlist.size(); ++i){
  mindex = idxlist(i);
  m.row(mindex) = do something with the matrix at m( idxlist(i) )
 }
}


The index list doesn't have any kind of constant stride or even order, so it might be like 2,9,1084,3,0,12 .... in order to tell the function to access those matrix elements only.

Is there any way I can create a map into to the matrix with very specific indices?

Bump... is the silence a "no"?

I missed it, the answer is indeed not yet.