problem geting velocity and acceleration

Hi

I have have a vector expressing position at 1 kHz and want to extract velocity and acceleration.

This is how I am doing it:

vel = diff(data)
acc = diff(data,2)

and this is what I am getting

How can I get a more useful estimation of velocity and ACC ? I have tried downplaying the data,but it doesn't help much.

Attached is the vector

Thanks

[Bob Thompson]

What defines a 'useful estimation'? Your plots are very cluttered, but not incorrect, as you have effectively taken the first and second derivatives of position, which are velocity and acceleration respectively.

[dpb]

Look at

doc gradient

to be able to account for the timestep between samples.

The plots show (as does the recorded position plot) that you've got a pretty-near constant triangle-wave position vector; hence the velocity is going to be approximately a constant +/- for each side of the ramp. There's some minor fluctuations observable that aren't visible in the full-band plots, but if you zoom in on the first section alone, then the changes will be more obvious.

What, specifically, is the end result you're looking for?