For each variable, the root-mean-square difference between the value read
from the variable's contour lines at each sample's biplot position (as
predict.prinsurf does) and the sample's actual value. This
measures how accurately a variable can be recovered by reading its contours,
combining the surface's lack of fit for that variable with the small loss
from interpolating between contour lines; lower is better, in the units of
the working data. Samples that fall outside the supported part of the
contour grid cannot be read and are excluded; their number is returned as the
attribute "n.unread".
Value
A named numeric vector of per-variable RMS contour-reading errors,
with the mean over all variables as the attribute "overall" and the
number of unreadable samples as the attribute "n.unread".
See also
predictivity for whole-sample reconstruction.