MATLAB: Mu law compressor function

MATLABmu law compressor

i have sawtooth function when i compress the function using this function

the matlab give me error

my code T = 10*(1/50); Fs = 10000; dt = 1/Fs; t = 0:dt:T-dt; x4 = sawtooth(2*pi*50*t);

 Xc = (log(1 + 255*abs(x4)) / log(1+u)) * sign(x4);

 T = 10*(1/50);
Fs = 10000; 
dt = 1/Fs;
t = 0:dt:T-dt; 
x4 = sawtooth(2*pi*50*t);
u=255
   Xc = (log(1 + 255.*abs(x4)) ./ log(1+u)) .* sign(x4)

   T = 10*(1/50);
  Fs = 10000; 
  dt = 1/Fs;
  t = 0:dt:T-dt; 
  x4 = sawtooth(2*pi*50*t);
  u=255
  expander = ((-1 + (1+u).^abs(x4)) ./ u);

T = 10*(1/50); 
Fs = 1000; 
dt = 1/Fs; 
t = 0:dt:T-dt;
x = sawtooth(2*pi*50*t);
plot(t,x)
xlim([0 0.2])
ylim([-1 1])
grid on