plot2d not working with negative values and 0



This doesn't work:

plot2d([x^(1/3) ], [x,-3,-2])$

> plot2d: expression evaluates to non-numeric value everywhere in
plotting range.

But:
x:-3; x^(1/3);float(%), numer;kill(x)$
-1.442249570307408

x:-2; x^(1/3);float(%), numer;kill(x)$
-1.259921049894873

Also:

If the x value is changed to a positive number,
values above 0 are plotted, 0 shows as a vertical
line, and nothing appears below 0.

plot2d([x^(1/3) ], [x,-3,0])$

> plot2d: expression evaluates to non-numeric value somewhere in
plotting range.