Hi

This seems so trivial, but I cannot figure out how to do it:

I have a vector v = [ 1 2 3 4 5 ]', and would like to reorder the elements, e.g. Have the 3 last elements be v(1:3), and the first two become v(4:5). in matlab, I could do v = [ v(3:end); v(1:2) ].

If I simply try:

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Eigen::VectorXd v(5);
v << 1,2,3,4,5;

v << v.tail(3), v.head(2);


I get aliasing (as would be expected).

This works:

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v << (Eigen::Vector3d() << v.tail(3)).finished(), (Eigen::Vector2d() << v.head(2)).finished();

but is really ugly.
Is there a simple way to copy/replace elements like that?

Thanks!

You can build a PermutationMatrix:

PermutationMatrix<Dynamic,Dynamic> p(5);
p.indices() << 3,4,0,1,2;
v = p*v;