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pythonarraysnumpyderivative
abcd
abcd

Reputation: 10751

Understanding numpy.gradient

I have a time-series of voltage values recorded in mV every 0.02 ms, stored as a numpy array.

If I do this,

dv_dt = np.gradient(v),

what will the units of dv_dt be? Will it be some multiple of V/s; e.g. mV/s, mV/(0.02 ms), etc?

My understanding is that gradient returns the derivative of the argument passed to it. Is that right?

See this related question.

Upvotes: 2

Views: 2289

Answers (1)

Moritz
Moritz

Reputation: 5408

Watch out for the unit spacing of dt. As noted in the documentation gradient assumes unit spacing of 1 unless you provide the sample distance by the vararg argument. Your case is only correct, if dt = 1 for all datapoints.

You have to define your units by yourself. It is fine to use milliseconds but unless you do not have a good reason for it, I would use SI units (in this case seconds and Volts; which is the same as mV and ms). The gradient will have units of mV/ms or V/s.

In your case np.gradient(v,0.02) will give you the first order difference of the voltage signal corrected with your spacing of the time axis.

Upvotes: 2

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