Arguments
enma
an object of class "enma" obtained from function
    nma.pdbs.
ncore
number of CPU cores used to do the calculation.
    ncore>1 requires package parallel installed.
a
a list object with elements U and L
    (e.g. as obtained from function nma) containing the
    eigenvectors and eigenvalues, respectively, to be 
    compared with b.
b
a list object with elements U and L
    (e.g. as obtained from function nma) containing the
    eigenvectors and eigenvalues, respectively, to be 
    compared with a.
subset
the number of modes to consider.
...
arguments passed to associated functions.