Indexing error using ezplot

Hi, I'm writing a code that uses symbolic variables and ezplot. My equation contains 17 variables, and I am trying to find the derivative with respect to 16 of the 17 variables. I'm not sure if I'm approaching this the correct way. My current code takes the derivative of the equation, then I use the subs command to put in values for the other variables, then use ezplot to show the derivative. Here's a portion of my code:

syms gamma02 gamma13 Gamma02 Gamma13 tau02 tau13 Omega02 Omega13 ...
    Phi02 Phi13 gamma02_1 gamma13_1 t;

gamma02 = Gamma02*cos(2*pi*tau02*t+Omega02)+Phi02;
gamma02_1 = Gamma02*cos(Omega02)+Phi02;
gamma13 = Gamma13*sin(2*pi*tau13*t+Omega13)+Phi13;
gamma13_1 = Gamma13*sin(Omega13)+Phi13;

syms Gamma02_e Gamma13_e tau02_e tau13_e Omega02_e Omega13_e Phi02_e Phi13_e psi;

U = Gamma13_e/Gamma02_e*(gamma02_1-Phi02_e)*exp(-1i*(Omega13_e-Omega02_e))+1i*(gamma13_1-Phi13_e);
theta_offset = 2*atan((sqrt(real(U).^2+imag(U).^2)-real(U))./imag(U));

U = (Gamma13_e/Gamma02_e*(gamma02-Phi02_e)*exp(-1i*(Omega13_e-Omega02_e))+1i*(gamma13-Phi13_e))*exp(1i*-theta_offset);
theta = 2*atan((sqrt(real(U).^2+imag(U).^2)-real(U))./imag(U));

syms theta_ref theta_err theta_err_rms;

theta_ref = atan(sin(2*pi*tau13*t),cos(2*pi*tau02*t));
theta_err = theta - theta_ref;
theta_err_rms = sqrt(mean(theta_err.^2));

syms dGamma02 dtau02 dOmega02 dPhi02;

dGamma02 = diff(theta_err_rms,'Gamma02');
dtau02 = diff(theta_err_rms,'tau02');
dOmega02 = diff(theta_err_rms,'Omega02');
dPhi02 = diff(theta_err_rms,'Phi02');

dGamma02 = subs(dGamma02,{Gamma02,Gamma13,Gamma13_e,tau02,tau02_e,tau13,tau13_e,Omega02,Omega02_e,Omega13,Omega13_e,Phi02,Phi02_e,Phi13,Phi13_e,t},{1,1,1,1/22,1/22,1/22,1/22,0,0,0,0,0,0,0,0,1});
ezplot(dGamma02);

As you can see, I take the derivative with respect to Gamma02, and that is the only variable I don't substitute with a number. The error I receive is this:

Error: ()-indexing must appear last in an index expression.

Error in ==> inline.feval at 36
        INLINE_OUT_ = inlineeval(INLINE_INPUTS_,
        INLINE_OBJ_.inputExpr, INLINE_OBJ_.expr);

Error in ==> ezplotfeval at 54
    z = feval(f,x(1),y(1));

Error in ==> ezplot>ezimplicit at 258
    u = ezplotfeval(f, X, Y);

Error in ==> ezplot at 155
                hp = ezimplicit(cax, f{1}, vars, labels, args{:});

Error in ==> sym.ezplot at 45
   h = ezplot(char(f));

I'm not too familiar with using symbolic variables, so maybe I am overlooking something simple. Thanks for the help.

Entire code uploaded to pastebin: http://pastebin.com/ktxUvm6L

[Oleg Komarov]

As you stated you have given us the partial code thus I am not able to reproduce the problem. You have to post all the relevant part such that contributors can test it.

Also, you should try to be concise, which could mean to post ONLY the relevant parts.

[Sean de Wolski]

What does char(f) evaluate to?

[Oleg Komarov]

I don't any problems on R2012a Win Xp 32b