Warning: Imaginary parts of complex X and/or Y arguments ignored

Hi eveyone,

I am not an experienced Matlab user at all and I don't understand why I am getting this error. I had this code work before in another program but when I changed the graphing interval from (-1,(pi/2)) to (-pi,pi) I got this error. The code that I had run before looks like this

 f = log(1+x);
T=taylor(f,'order',6);
pretty(T)
figure()
x_values=linspace(-1,(pi/2));
f_values = log(1+x_values);
T_values=subs(T,x_values);
plot(x_values,f_values);
hold on; plot(x_values,T_values,':');

All I did for the new code was change the interval from (-1,(pi/2)) to (-pi,pi) and changed the degree of the taylor polynomial from 5 to 7.

 f = log(1+x);
T=taylor(f,'order',8);
pretty(T)
figure()
x_values=linspace(-pi,pi);
f_values = log(1+x_values);
T_values=subs(T,x_values);
plot(x_values,f_values);grid on;
hold on; plot(x_values,T_values,':');

I am getting the error for the f_values = log(1+x_values) part and I don't understand why I am. If someone could please help out it would be great because I have no clue what I am doing or why this isn't working. Thanks so much!

Answer 1

[Torsten]

(1-pi) < 0, so log(1+x) does not return real values.

Best wishes

Torsten.