why my plot is not correct?

here is my code

x = -5:0.1:5

y = x.^(1/3)

plot(x,y)

[wenchong chen]

it is working, but it is giving me wrong number

[wenchong chen]

also there is a Warning: Imaginary parts of complex X and/or Y arguments ignored.

Answer 1

[Paul]

If you're looking for a plot with odd symmetry, try:

plot(x,nthroot(x,3))  % check doc nthroot for details

Answer 2

[DGM]

I'm not sure what you intend the correct number to be. You're doing the cube root of negative numbers. They're going to be complex.

By default, plot() will only plot the real component of complex inputs. If you're expecting the plot to be symmetrical, consider plotting abs(y) to get the magnitude of the complex-valued region.

x = -5:0.1:5;
y = x.^(1/3);
h1=plot(x,real(y)); hold on
h2=plot(x,imag(y));
h3=plot(x,abs(y));
legend([h1,h2,h3],'real','imaginary','magnitude','location','southeast')

[wenchong chen]

the^1/3 of negative numbers should be negative right? why both negative and positive side are both positive number?

[DGM]

You probably want Paul's answer below. nthroot() calculates the real root, whereas power() or .^ calculates the complex root. The web docs include such an example.