Velocity from acceleration data

Hi all,

I have an acceleration data from accelerometers. I want to get velocity from the data by integrate it using matlab. Here my coding :-

%clear

clc;

%Create a baseline sinusoidal signal

ch1_100mss = ch1_100ms
xdata = ch1_100mss;
y0 = sin(xdata);

%Add noise to the signal

noise = 2*y0.*randn(size(y0));    % Response-dependent 

ydata = y0 + noise;               % Gaussian noise

% %Fit the noisy data with a custom sinusoidal model

f = fittype('a*sin(b*x)');
fit1 = fit(xdata,ydata,f,'StartPoint',[1 1]);

%Find the integral of the fit at the predictors

int = integrate(fit1,xdata,0);

%Plot the data, the fit, and the integral

subplot(2,1,1)
plot(fit1,xdata,ydata)    % cfit plot method
subplot(2,1,2)
plot(xdata,int,'m')      % double plot method
grid on
legend('integral')
plot(fit1,xdata,ydata,{'fit','integral'})

and the plot is

my question are:-

1) When i run the coding below warning is appear

      Warning: Minimum step size reached; singularity possible.
  > In quad at 103
    In cfit.integrate at 42
    In integration at 23
  Warning: Minimum step size reached; singularity possible.
  > In quad at 103
    In cfit.integrate at 40
    In cfit.plot at 138
    In integration at 33
  Warning: Minimum step size reached; singularity possible.
  > In quad at 103
    In cfit.integrate at 42
    In cfit.plot at 138
    In integration at 33

is my result valid???

2) What the velocity value from the graph?

Thank you.