  The Einstein field equations, or generalizations thereof, are difficult to
solve analytically. On the other hand, numerical solutions of the same
equations have become increasingly common, in particular concerning compact
objects. Whereas analytic approximations to each individual solution within a
numerical family have been proposed, proxies for whole families are missing,
which can facilitate studying properties across the parameter space, data
compression and a wider usage of such solutions. In this work we tackle this
need, proposing a simple strategy based on a double expansion of the unknown
functions in an appropriately chosen basis, to build such proxy. We use as an
exploratory case-study spherical, fundamental mini-boson stars, to illustrate
the feasibility of such an approach, emphasise its advantage in reducing the
data size, and the challenges, say, in covering large parameter spaces.
