MATLAB Legend Color and semilogy() Plotting Problems

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Kody
Kody 2013-10-27
回答： Walter Roberson 2013-10-27
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;

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采纳的回答

Walter Roberson
Walter Roberson 2013-10-27
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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