The  polynomial controlled sources call a poly function that evaluates a polynomial computed from a vector of signals, $\left[s_1\,s_2\,\mathrm{...}\,s_n\right]$, and a vector of coefficients, $\left[a_0\,a_1\,\mathrm{...}\right]$ using the following formula.

The coefficients given as $a_{\cdot }$ correspond to sequential locations in the vector of coefficients.

If the vector of coefficients contains only one element, $\left[a_0\right]$, the evaluated polynomial is $\mathrm{poly}\=a_0{s}_1$, not $\mathrm{poly}\=a_0$.