plot using user custumized legend lines

Hello all!

I wanted to change the color of the legend lines in order to have the same colors of the plotted circles in the graph (here each circle is presenting the radius calculated using K variable). I tried different methods but not worked. Please find the graph and my code attached. Thank you in advance.

K = [100;200;400;600;800;1000;1200;1400;1600;1800;2000];
a = 1;
B=0.2;

r = radius_cal (K,B) ;

figure
yline(0)

hold on
for i=1 :1: length(r)
    circle (0,0,r(i));
    hold on
    xline (r(i))
    hold on
end
hold on 
yline (a,'Color','b')
fontSize = 14;
xlabel('radius')
legend({'100','200','400','600','800','1000','1200','1400','1600','1800','2000'})
grid minor

function r = radius_cal (K,B)
E0= my_const.m_mu_kg .* my_const.C .* my_const.C .* 6241506479963.2 ;
gamma = 1+ (K ./ E0);
v =  my_const.C * sqrt (1- (1./(gamma .* gamma)));
omega= ((my_const.q .* B) ./ my_const.m_mu_kg) .* sqrt (1- (v .* v) ./ (my_const.C .* my_const.C) );
r= v ./ omega;
end

function circle(x,y,r)
ang=0:0.001:2*pi / 4; 
xp=r*cos(ang);
yp=r*sin(ang);
plot(x+xp,y+yp);
end

Answer 1

[Voss]

The set of colors of the lines in the legend doesn't match with the set of colors of the circles because the xlines and ylines are also being used in the legend. To fix that, you can make the legend based on the circles only.

K = [100;200;400;600;800;1000;1200;1400;1600;1800;2000];
a = 1;
B=0.2;

r = radius_cal (K,B) ;

figure
hold on % (you can do "hold on" only once, at the top)
yline(0)
h = zeros(1,numel(r)); % h: array of circle lines
for i = 1:numel(r)
    h(i) = circle (0,0,r(i),K(i));
    xline (r(i))
end
yline (a,'Color','b')
fontSize = 14;
xlabel('radius')
legend(h) % legend based on the lines in h only
grid minor

function r = radius_cal (K,B)
E0= my_const.m_mu_kg .* my_const.C .* my_const.C .* 6241506479963.2 ;
gamma = 1+ (K ./ E0);
v =  my_const.C * sqrt (1- (1./(gamma .* gamma)));
omega= ((my_const.q .* B) ./ my_const.m_mu_kg) .* sqrt (1- (v .* v) ./ (my_const.C .* my_const.C) );
r= v ./ omega;
end

function h = circle(x,y,r,K)
% pass in a K value to be used as the DisplayName 
% of the line (for the legend)
ang=0:0.001:2*pi / 4; 
xp=r*cos(ang);
yp=r*sin(ang);
% return the plotted line (h):
h = plot(x+xp,y+yp,'DisplayName',num2str(K));
end

[Hamid]

Thanks a lot! That was very helpful.

[Voss]

You're welcome!

Answer 2

[KSSV]

K = [100;200;400;600;800;1000;1200;1400;1600;1800;2000];
a = 1;
B=0.2;

r = radius_cal (K,B) ;
c = {'r','g','b','c','m','y','k'} ;  % specify your colors here.. length of c should be equal to length of r
figure
yline(0)

hold on
for i=1 :1: length(r)
    [xp,yp] = circle (0,0,r(i));   % <---- get the coordinates of the circle
    plot(xp,yp,'color',c{i})    %<---- plot the circle with specified colors in cell array c 
    xline (r(i))    
end
hold on 
yline (a,'Color','b')
fontSize = 14;
xlabel('radius')
legend({'100','200','400','600','800','1000','1200','1400','1600','1800','2000'})
grid minor



function r = radius_cal (K,B)
E0= my_const.m_mu_kg .* my_const.C .* my_const.C .* 6241506479963.2 ;
gamma = 1+ (K ./ E0);
v =  my_const.C * sqrt (1- (1./(gamma .* gamma)));
omega= ((my_const.q .* B) ./ my_const.m_mu_kg) .* sqrt (1- (v .* v) ./ (my_const.C .* my_const.C) );
r= v ./ omega;
end
% Function is changed so that, it will give the coordinates of circle. 
function [xp,yp] = circle(x,y,r)
ang=0:0.001:2*pi / 4; 
xp=r*cos(ang);
yp=r*sin(ang);
end

[Hamid]

Thank you so much.