The curve fiutting toolbox in Matlab includes the function smooth(). By default, smooth applies a moving average filter to the data. You can specify the span, which is the width, in points, of the moving average. Example:
y=sin(2*pi*(0:99)/100)+rand(1,100); % noisy signal
span=5;
yy=smooth(y,span); % smoothed signal
plot(0:99,y,'-r',0:99,yy,'-b')
legend('Raw','Smoothed, span=5')
I am not familiar with the smoothing function you used in R, or the meaning of span for the smoothing routine in R. It could be very similar to Matlab's smooth(), as illustrated above.
