struct covariance *
covariance_2pass_create (size_t n_vars, const struct variable **vars,
size_t n_catvars, const struct variable **catvars,
const struct variable *weight, enum mv_class excl);
void covariance_accumulate (struct covariance *, const struct ccase *);
struct covariance *
covariance_2pass_create (size_t n_vars, const struct variable **vars,
size_t n_catvars, const struct variable **catvars,
const struct variable *weight, enum mv_class excl);
void covariance_accumulate (struct covariance *, const struct ccase *);