Compute (truncated) orthonormal eigenfunctions and scores for data potentially on a non-equidistant grid.
fpc_wsvd(data, arg, pve = 0.995)
numeric matrix of function evaluations (each row is one curve, no NAs)
numeric vector of argument values
percentage of variance explained
a list with entries
`mu`` estimated mean function (numeric vector)
`efunctions`` estimated FPCs (numeric matrix, columns represent FPCs)
scores estimated FPC scores (one row per observed curve)
npc how many FPCs were returned for the given
code adapted from / inspired by
wsvd() function of Bioconductor
mogsa by Cheng Meng.