function campo_RJ

a=input('Parametro a:');
b=input('Parametro b:');


[x,y] = meshgrid(-0.3:.05:0.3,-0.3:.05:0.3);
u=zeros(size(x));
v=zeros(size(x));
for i=1:max(size(x)),
    for j=1:max(size(x)),
        u(i,j)= a*x(i,j)+b*y(i,j);
        v(i,j)= b*x(i,j)+a*y(i,j);
 %       u(i,j)= a*y(i,j);
 %       v(i,j)= -b*x(i,j);
    end
end
quiver(x,y,u,v),shg