struct covariance * covariance_1pass_create (size_t n_vars, const struct variable *const *vars,
const struct variable *wv, enum mv_class excl);
struct covariance *
covariance_2pass_create (size_t n_vars, const struct variable *const *vars,
struct covariance * covariance_1pass_create (size_t n_vars, const struct variable *const *vars,
const struct variable *wv, enum mv_class excl);
struct covariance *
covariance_2pass_create (size_t n_vars, const struct variable *const *vars,