How to present the boundary of country and vectors?

Hi, I'd like to present my data in mercator projection. It's a set of vectors. I used m_map package. The problem is that my shapefile doesn't show, only vectors. My code is below. How to present the boundary of country and vectors? Please help!

wek=importdata('wektory.txt'); % U and V

mapa=importdata('mapa.txt'); %points with lon, lat

m_proj('mercator','lon',[14 26],'lat',[48 56]);

m_shaperead('poland');

m_grid;

m_quiver(mapa(:,3),mapa(:,2),wek(:,2),wek(:,3));