how to solve low-level graphics?

I want to slove the error about low-level graphics.

Could you help me?

Theta_Theory = linspace(D2, D1, 10000);     
Velocity_Theory = linspace(-100,0,10000);          
figure(1);
[Theta_Theory, Velocity_Theory] = meshgrid(Theta_Theory, Velocity_Theory);
x1 = sin(Theta_Theory);  
y1 = -cos(Theta_Theory);
T =  sqrt(2*abs(y1)/9.8); 
target = 10;
S_z = x1 + abs(Velocity_Theory.*cos(Theta_Theory)).*T.';
z = -abs(S_z -target);
h = pcolor(Theta_Theory, Velocity_Theory,z);
shading interp
set(h,'EdgeColor','none','linestyle','none');
colorbar;
colormap(jet(256));