of <code>~</code>.  By default,
an intercept is included. If no intercept, <code>-1</code> should be the first
term included on the right of <code>~</code>.</p></dd>


<dt id="arg-mixture">mixture<a class="anchor" aria-label="anchor" href="#arg-mixture"></a></dt>
<dd><p>one-sided formula object for the class-specific fixed effects
in the linear mixed model (to specify only for a number of latent classes
greater than 1).  Among the list of covariates included in <code>fixed</code>, the
covariates with class-