derivative of non equal space in time

[sujju]

Hi,

I want to find 1st and 2nd derivative of an array.

The time spacing is not equal , and i need non-equal time space for my application.

Can any one suggest the easy way to do it?

[GerdW]

Hi sujju,

what about applying simple math like dx/dt?

How are your array elements arranged to have "non equal time spacing"?

[sujju]

Hi,

I tried with simple maths dx/dt and used  Derivativex(t).vi  with backward differenciation bt its not giving me good result.

[johnsold]

Please be more specific than "not giving me good result." What is not good about the result? Does it not generate any result? Is the result incorrect by 1%? Is the result noisy? Is the result the wrong shape?

The signal you have drawn is likely discontinuous at points B and E, so some non-smooth result would be expected there.

How many points are in each segment?

Consider the Savitsky-Golay filter for calculating the derivatives. I think someone, possibly Dr. Gray, posted a link to a means of using it on unequally spaced data. 

Reampling or other  forms of interpolation may be useful also.

Lynn

[sujju]

Thank u..

Will try with Golay technique.