Suppose I have two vectors of doubles, where one of them is supposed to store a subset of entries of the other:

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VectorXd vec(5), subvec(3);


Suppose the subset is determined by a vector of indexes:

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VectorXi id(3);


Is there a way in Eigen to work with a wrapper for the larger vector such that operations like:

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for(i = 0; i < 3; ++i)
   vec[id[i]] = subvec[i];


become:

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for(i = 0; i < 3; ++i)
   vec_wrapper[i] = subvec[i];


Its like a permutation view of the larger vector. Note that vec_wrapper would hold some reference to the vec data.

this is a common feature request, unfortunately nobody took the time to implement it yet. Actually you would even write:

vec(id) = subvec;