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Are MATLAB's window functions incorrect (starting at n = 1 instead of n = 0)?

Asked by Miles Henrichs on 20 Mar 2019
Latest activity Answered by Jan
on 20 Mar 2019
According to Wikipedia's page on window functions, the first value of most of these functions should be 0. For example, triangular windows are defined for 0 <= n <= N - 1.
In contrast, MATLAB's windowing functions (I'll use triang() as an example) define the window for 1 <= n <= N.
triangular_window = triang(10); % first value is 0.1, not 0
Is this incorrect? If not, why?

  2 Comments

I suspect this has something to do with Matlab being a 1 index language, instead of 0 index (which is the majority of the programming languages).
Have a look at all the values. Compare with triang(9). Think about what contribution first and last-element with zero in them would contribute to in filtering and whether you need to drag those through the calculations...
HTH

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1 Answer

Answer by Jan
on 20 Mar 2019

The documentation is clear in this point: https://www.mathworks.com/help/signal/ref/triang.html#bt6p4f0
The triangular window is very similar to a Bartlett window. The Bartlett window always ends with zeros at samples 1 and L, while the triangular window is nonzero at those points.
w(n) = (2*n-1) / L for 1<=n<=L/2
Does this clarify your question?

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