function barycentres(Coord,C,i,j);
// preparation du graphique  
  xbasc();           								
  deltax=(max(Coord(:,i))-min(Coord(:,i)))/20;
  xmin=min(Coord(:,i))-deltax;
  xmax=max(Coord(:,i))+deltax;
  deltay=(max(Coord(:,j))-min(Coord(:,j)))/20;
  ymin=min(Coord(:,j))-deltay;
  ymax=max(Coord(:,j))+deltay;
  plotframe([xmin,ymin,xmax,ymax],[2,10,2,10],[%f,%f],..
			["Projection sur le plan "+string(i)+"-"+string(j),"",""]);
  plot2d([0,0],[ymin,ymax],2,"000");
  plot2d([xmin,xmax],[0,0],2,"000");
  
  // modalités
  mod=['C','Z'];
  
  // representation des individus suivant leur modalite
  for k=mod,
	I=find(C==k);
	B=mean(Coord(I,:),"r");
	B=B'.*.[1,0];
	B=B'
	plot2d(B(:,i),B(:,j),5,"000");
	plot2d(B(:,i),B(:,j),-1,"000");
	xset("font",2,3);
	xstring(B(1,i),B(1,j),k);
	xset("font",2,1);
	for l=I,
	  xstring(Coord(l,i),Coord(l,j),k);
	end;
  end;
endfunction;