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