Third flattening of ellipse from eccentricity
n = ecc2n(ecc)
n = ecc2n(ellipsoid)
n = ecc2n(ecc) computes the parameter n (the "third flattening") of an ellipse (or ellipsoid of revolution) given its eccentricity ecc. n is defined as (a-b)/(a+b), where a is the semimajor axis and b is the semiminor axis. Except when the input has 2 columns (or is a row vector), each element is assumed to be an eccentricity and the output n has the same size as ecc.
n = ecc2n(ellipsoid), where ellipsoid has two columns (or is a row vector), assumes that the eccentricity is in the second column, and a column vector is returned.