Why is the derivative of a function or signal one sample shorter that the orignal?
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Hi All
taking the derivative of y=x.^2 using diff(y) , between 0 and 100 gives a signal with one less Sample, meaning instead of length of 101, it is 100 samples. so every derivative, it will get one sample shorter and if I have to integrate again, it will need those samples again maybe ? what should I do ?
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Accepted Answer
Star Strider
on 11 Apr 2020
Use the gradient function to calculate the numerical derivatives. The output will be the same length as the input. (It is also more accurate in that respect.) The function assumes regularly-sampled data, however if the sampling intervals are not constant, a work-around for that is:
dydx = gradient(y) ./ gradient(x);
.
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Cris LaPierre
on 11 Apr 2020
diff is taking the difference between adjacent data points. Because the difference is between two points, this causes the result to be one data point shorter.
For a simple array x=[3 4 5], diff(x)=[4-3 5-4] = [1 1].
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