filter function automatically checks periodicity of X

I'm just wondering if the filter function already checks if the input signal/sequence you entered is periodic or aperiodic. I mean if I enter this for example:

Periodic sequence of [1 2 9 10]

Aperiodic sequence of [ 5 6 7 8 0 0 0 0 0...]

MATLAB would just recognize both as [1 2 9 10] and [5 6 7 8] respectively right? How can the filter function detect the periodicity of the input? Or is DFT just used (since it can be used on both periodic and aperiodic signals)

[Guillaume]

Which filter function are you talking about?

The filter function does not care one bit about the shape of the input. It applies the filter to all elements, including 0s. It knows nothing about periodic or aperiodic.

[Riven Yvet]

What does the filter does anyway, convolution in the time domain or convolution in the frequency domain (DFT)?

Answer 1

[Jan]

Here you find a M-verion of the filter command: http://www.mathworks.com/matlabcentral/answers/9900-use-filter-constants-to-hard-code-filter#answer_13623 . It is a "direct form II transposed" method as explained in the documentation: doc filter: More about