Legend Producing Wrong Colour Lines

Hi I have been trying to plot multiple lines on the same plot and the colours of the lines are coming up incorrectly. Here is my code and the results. I am currently running 2020b

plot(x,freal,'k')

hold on

plot(x,ftaylor0,'r')

plot(x,ftaylor1,'b')

plot(x,ftaylor2,'g')

plot(x,ftaylor3,'m')

plot(x,ftaylor4,'c')

hold off

legend('f(x)', 'p0(x)', 'p1(x)', 'p2(x)', 'p3(x)', 'p4(x)')

xlabel('x')

ylabel('f(x)')

[VBBV]

can you provide the full code ?

[Alyssa Neale]

x=-5:0.1:5;

freal=x.*exp(-x);

ftaylor0= 1/exp(1);

ftaylor1= 1/exp(1);

ftaylor2= (1/exp(1))-(1/(2*exp(1)).*(x-1).^2);

ftaylor3= (1/exp(1))-(1./(2.*exp(1)).*(x-1).^2)+((1./(3.*exp(1))).*(x-1).^3);

ftaylor4= (1/exp(1))-(1./(2.*exp(1)).*(x-1).^2)+((1./(3.*exp(1))).*(x-1).^3)-((1./(8.*exp(1))).*(x-1).^4);

Answer 1

[VBBV]

x=-5:0.1:5;
freal=x.*exp(-x);
ftaylor0= 1./exp(x); %  they is scalar in your code
ftaylor1= 1./exp(-x);  % this is scalar in your code 
ftaylor2= (1/exp(1))-(1/(2*exp(1)).*(x-1).^2);
ftaylor3= (1/exp(1))-(1./(2.*exp(1)).*(x-1).^2)+((1./(3.*exp(1))).*(x-1).^3);
ftaylor4= (1/exp(1))-(1./(2.*exp(1)).*(x-1).^2)+((1./(3.*exp(1))).*(x-1).^3)-((1./(8.*exp(1))).*(x-1).^4);
plot(x,freal,'k')
hold on
plot(x,ftaylor0,'r')
plot(x,ftaylor1,'b')
plot(x,ftaylor2,'g')
plot(x,ftaylor3,'m')
plot(x,ftaylor4,'c')
hold off
legend('f(x)', 'p0(x)', 'p1(x)', 'p2(x)', 'p3(x)', 'p4(x)')

You can see ftaylor0 and ftaylor1 are scalars with just one point. You need to make them vectors

[VBBV]

x=-5:0.1:5;
freal=x.*exp(-x);
ftaylor0= 1./exp(1) %  they is scalar in your code

ftaylor0 = 0.3679

ftaylor1= 1./exp(1)  % this is scalar in your code 

ftaylor1 = 0.3679

ftaylor2= (1/exp(1))-(1/(2*exp(1)).*(x-1).^2);
ftaylor3= (1/exp(1))-(1./(2.*exp(1)).*(x-1).^2)+((1./(3.*exp(1))).*(x-1).^3);
ftaylor4= (1/exp(1))-(1./(2.*exp(1)).*(x-1).^2)+((1./(3.*exp(1))).*(x-1).^3)-((1./(8.*exp(1))).*(x-1).^4);
plot(x,freal,'k')
hold on
plot(ftaylor0,'>r','MarkerSize',10)  % use a marker to plot 
plot(ftaylor1,'sb','MarkerSize',4)  % use a marker to plot 
plot(x,ftaylor2,'g')
plot(x,ftaylor3,'m')
plot(x,ftaylor4,'c')
hold off
legend('f(x)', 'p0(x)', 'p1(x)', 'p2(x)', 'p3(x)', 'p4(x)','location','best')

You can also plot them as data point with proper legend