FEM matlab( mesh generation for rectangular geometry with empty space )

Dear all i want to generate triangular mesh for a rectangular having empty space in center. i had created rectangular empty space by using inpolygon command

[in on]=inpolygon(x,y,vx, vy)

The triangular mesh had been generated by using command delaunay

t=delaunay(x,y)

The problem i am facing is that the all the boundary node of empty space are connected with each other so instead of an empty space i am getting some mesh for boundary nodes. My question is how can i eliminates these boundary nodes

Best regards