The paper considers approximations of first-
and second-order moments of random functions
with values in a high-dimensional Euclidean
space using projections onto suitable
low-dimensional linear submanifolds. To
quantify the goodness of the approximation a
criterion based on the mean squared Euclidean
distance is introduced. In case of
wide-sense stationary random functions optimal
low-dimensional linear submanifolds are given
in terms of the mean
vector and eigenvectors of the variance matrix.
Keywords :
random vector process, low-dimensional approximation, optimal projection