Undefined function or method 'fitoptions' for input arguments of type 'char' ?

Having trouble using fitoptions function:

Undefined function or method 'fitoptions' for input arguments of type 'char'

r=r.*33.*.5;
theta=theta.*(pi/180)+pi/2;
[x,y,zz] = pol2cart(theta,r,z);

ft = 'linearinterp';
opts = fitoptions( ft );
opts.Normalize = 'off';
[fitresult, gof] = fit( [x, y], zz, ft, opts  );

[EDITED, Jan, please format you code - Thanks]

Answer 1

[Jan]

Do you have the Curve Fitting Toolbox? See output of:

ver