_l  a_{il}  q_{il} t_l ( \bold{ \theta_{p} } )   - b_{i} ) $$
with known functions \(t_l\) of the trait vector \(\bold{\theta}_p\).
Fixed values of the functions \(t_l\) are specified in the
\(\bold{\theta}_p\) design matrix <code>theta.kDES</code>.</p>
<p>The partially compensatory item response model (<code>irtmodel="partcomp"</code>)
is defined by
$$P(X_{pi}=1 | \bold{\theta}_p )=c_i + (d_i - c_i )
\frac{ \exp \left( \sum_l ( a_{il}  q_{il} \theta_{pl} - b_{il} ) \right) }
{  \mu_i \prod_l ( 1 + \exp ( a