This is a modified version of `cmdscale`

that uses the Lanczos
procedure (`slanczos`

) instead of `eigen`

. Called by
`smooth.construct.pco.smooth.spec`

.

`cmdscale_lanczos(d, k = 2, eig = FALSE, add = FALSE, x.ret = FALSE)`

d

a distance structure as returned by `dist`

, or a full
symmetric matrix of distances or dissimilarities.

k

the maximum dimension of the space which the data are to be
represented in; must be in `{1, 2, ..., n-1}`

.

eig

logical indicating whether eigenvalues should be returned.

add

logical indicating if the additive constant of Cailliez (1983) should be computed, and added to the non-diagonal dissimilarities such that the modified dissimilarities are Euclidean.

x.ret

indicates whether the doubly centred symmetric distance matrix should be returned.

as `cmdscale`

Cailliez, F. (1983). The analytical solution of the additive constant problem.
*Psychometrika*, 48, 343-349.