gap&gt; ps := PG(3,9);
ProjectiveSpace(3, 9)
gap&gt; sub := VectorSpaceToElement(ps,[[1,0,1,0],[0,1,0,1],[1,2,3,0]]*Z(3)^0);
&lt;a plane in ProjectiveSpace(3, 9)&gt;
gap&gt; p1 := VectorSpaceToElement(ps,[1,0,1,2]*Z(3)^0);
&lt;a point in ProjectiveSpace(3, 9)&gt;
gap&gt; p2 := VectorSpaceToElement(ps,[1,2,0,2]*Z(3)^0);
&lt;a point in ProjectiveSpace(3, 9)&gt;
gap&gt; phi := ElationOfProjectiveSpace(sub,p1,p2);
&lt; a collineation: &lt;cmat 4x4 over GF(3,2)&gt;, F^0&gt;
