MATLAB: MATLAB Legend Color and semilogy() Plotting Problems

legendsemilogy

I am new to MATLAB and am just recently building a simple program. Everything seems to work fine except my legend is only showing the color red for all 5 of my semilogy() plots and I am getting unnecessary line from my plots to the x intervals. I realize my code isn't very efficient. It is pretty much the same code looped 5 times except with different g values. How can I fix my legend colors to be different and to get rid of the lines in my graph running to the x intervals?
close all; clear; clc;
g1 = 0.5; g2 = 0.618; g3 = 0.7; g4 = 0.8; g5 = 0.9;
f = @ (x) 2*sin(x) - (x.^2/10);
it = 20;
tol = 0.0001;
xl = 0;
xu = 4;
xlabel('Iterations');
ylabel('Bracket Interval Size Pending G Value');
bs = zeros(20,1);
hold on;
for i = 1:it
    r1 = g1 * (xu - xl);
    deltax1 = 0.01 * r1;
      fl1 = f(xl + r1 - deltax1);
      fu1 = f(xl + r1 + deltax1);
      if fl1 > fu1
          xu = xl + r1;
      else
          xl = xl + r1;
      end
      bs(i) = xu - xl;
      semilogy(bs, 'r');
      if abs((fl1 - xl) / xl) < tol
          break
      end
  end
xl = 0;
xu = 4;
for i = 1:it
    r2 = g2 * (xu - xl);
    deltax2 = 0.01 * r2;
      fl2 = f(xl + r2 - deltax2);
      fu2 = f(xl + r2 + deltax2);
      if fl2 > fu2
          xu = xl + r2;
      else
          xl = xl + r2;
      end
      bs(i) = xu - xl;
      semilogy(bs, 'b');
      if abs((fl2 - xl) / xl) < tol
          break
      end
  end
xl = 0;
xu = 4;
for i = 1:it
    r3 = g3 * (xu - xl);
    deltax3 = 0.01 * r3;
      fl3 = f(xl + r3 - deltax3);
      fu3 = f(xl + r3 + deltax3);
      if fl3 > fu3
          xu = xl + r3;
      else
          xl = xl + r3;
      end
      bs(i) = xu - xl;
      semilogy(bs, 'k');
      if abs((fl3 - xl) / xl) < tol
          break
      end
  end
xl = 0;
xu = 4;
for i = 1:it
    r4 = g4 * (xu - xl);
    deltax4 = 0.01 * r4;
      fl4 = f(xl + r4 - deltax4);
      fu4 = f(xl + r4 + deltax4);
      if fl4 > fu4
          xu = xl + r4;
      else
          xl = xl + r4;
      end 
      bs(i) = xu - xl;
      semilogy(bs, 'g');
      if abs((fl4 - xl) / xl) < tol
          break
      end
  end
xl = 0;
xu = 4;
for i = 1:it
    r5 = g5 * (xu - xl);
    deltax5 = 0.01 * r5;
      fl5 = f(xl + r5 - deltax5);
      fu5 = f(xl + r5 + deltax5);
      if fl5 > fu5
          xu = xl + r5;
      else
          xl = xl + r5;
      end
      bs(i) = xu - xl;
      semilogy(bs, 'y');
      if abs((fl5 - xl) / xl) < tol
          break
      end
  end
xlabel('Iterations');
ylabel('Bracket Interval Size Pending G Value');
legend('g = 0.5', 'g = 0.618', 'g = 0.7', 'g = 0.8', 'g = 0.9');
hold off;

Best Answer

Move your semilogy() calls out of the "for" loops they are in, to after the end of each "for i" loop -- after, that is, you have calculated each entire "bs" vector.
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