Plot sine wave whose frequency changes with time

Hello.I want to plot a sine wave whose frequency changes with time. The equation is y=sin(2*pi*(50+g)*t) where g=sin(10*pi*t) My problem is ,when I plot the function y from t=0 to 2s, There are "zones" where it does not oscillate.So can some one point out where my mistake is ,thank you.I have been struggled at this point for days. Here is my code:

fs=1000        %Sampling frequency
Ts=1/fs        %Sampling period 
L=2000         %Sampling length (2000 points)
n=(0:L-1)*Ts   %Samples
for count_n=1:length(n)
  g(count_n)=sin(10*pi*n(count_n))
  y(count_n)=sin(2*pi*(50+g(count_n))*n(count_n))
  F(count_n)=50+g(count_n)          
end

Answer 1

[Grzegorz Knor]

t = linspace(0,2,2000);
plot(t,sin(2*pi*(50+sin(10*pi*t)).*t))