how do i include the one point in the complex plane in my legend

Hi all

im plotting gershgorin discs for eigenvalues with the following function

% gerschdisc.m
% 
% This function plots the Gershgorin Discs for the matrix A passed as an argument.
% It will also plot the centers of such discs, and the actual eigenvalues
% of the matrix.
function gershdisc(A)
A = [sqrt(-1) sqrt(2); sqrt(2) sqrt(-1)];
error(nargchk(nargin,1,1));
if size(A,1) ~= size(A,2)
    error('Matrix should be square');
    return;
end

% For each row, we say:
for i=1:size(A,1)
    % The circle has center in (h,k) where h is the real part of A(i,i) and
    % k is the imaginary part of A(i,i)   :
    h=real(A(i,i)); k=imag(A(i,i)); 

      % Now we try to compute the radius of the circle, which is nothing more
      % than the sum of norm of the elements in the row where i != j
      r=0;
      for j=1:size(A,1)
         if i ~= j 
             r=r+(norm(A(i,j)));
         end    
      end 

      % We try to make a vector of points for the circle:
      N=256;
      t=(0:N)*2*pi/N;

      % Now we're able to map each of the elements of this vector into a
      % circle:
      plot( r*cos(t)+h, r*sin(t)+k ,'-');

      % We also plot the center of the circle for better undesrtanding:
      hold on;
      plot( h, k,'+');
    end
    % For the circles to be better graphed, we would like to have equal axis:
    axis equal;
    % Now we plot the actual eigenvalues of the matrix:
    ev=eig(A);
    for i=1:size(ev)
      rev=plot(real(ev(i)),imag(ev(i)),'ro');
    end
    hold off;
    legend(rev,'Actual Eigenvalues',,'+');
    xlim([-3 3]);
    ylim([-3 3]);
  end

how do i include the center point and the circle in the legend?

Answer 1

[dpb]

Save the handles when you plot them--

...
hLCirc=plot(r*cos(t)+h, r*sin(t)+k ,'-');
hold on;
hLCntr=plot(h, k,'+');
...
legend([hLCirc hLCntr rev],'Circle','Center','Actual Eigenvalues',,'+');

See

doc legend  % for more concise ways to write the legend text w/ cellstr arrays, etc., ...

[martinkjr]

Thank u so much