polar plot error "Undefined function or variable 'polarplot'." Anyone help pls ?

I typed this code in my script, and the error i got is

Undefined function or variable 'polarplot'.

theta = 0:0.01:2*pi; rho = sin(2*theta).*cos(2*theta); polarplot(theta,rho)

when my ver is R2015a.

[Walter Roberson]

Duplicates http://www.mathworks.com/matlabcentral/answers/310248-i-have-a-excel-sheet-with-phase-angles-i-want-to-plot-a-polar-plot-only-with-the-phase-angles-can