function [xx yy Ex Ey] =  ldc2(qs, R)
% draws the Electric field around charges qs at position R
% qs is a  line vector of charge
% R is a matrix of [x1 x2 ...;y1 y2 ...]

Nc = length(qs);
L = 0.5; %draw around length

xqs = R(1,:);
yqs = R(2,:);

xmin = min(xqs);
xmax = max(xqs);

ymin = min(yqs);
ymax = max(yqs);

x = linspace(xmin-L,xmax+L,30);
y = linspace(ymin-L,ymax+L,30);
[xx yy] = meshgrid(x,y);
xx = xx(:);
yy = yy(:);


%remove points too close to the center of each charge
for k = 1:Nc
    d =(xx - xqs(k)).^2 + (yy - yqs(k)).^2;
    invalid = (d < 0.1);
    xx(invalid) = [];
    yy(invalid) = [];
end


Ex = zeros(length(xx),1);
Ey = zeros(length(yy),1);

for k = 1:Nc
    l = sqrt((xx-xqs(k)).^2 + (yy-yqs(k)).^2);

    E = qs(k)./(4.*pi.*l.^2);

    ux = (xx-xqs(k))./l;
    uy = (yy-yqs(k))./l;
    Ex = Ex + E .* ux;
    Ey = Ey + E .* uy;
end
quiver(xx,yy,Ex,Ey)