Derivative of noisy signal My input signal is phase vector. I want to differentiate it to get frequency vector. My input signal is somewhat noisy. Here is the input signal.


This is the derivative of the input signal as calculated using 

diff(inputSig)




When i differentiate this signal, I am not getting a smooth curve. 
The output looks 'spikey'. I am guessing it is because of the noise in the input signal (is this 'derivative kick'?). How to avoid this and get a smooth derivative curve?
2 point discrete differentiation is bound to produce highly noisy results.
try the 5-points stencil. you can also generate coefficients (i.e. more points) yourself using derivation of Lagrange polynomials.