I was confused with the concept of the filter corner.

What is filter corner mentioned in the following picture?

Check out the wikipedia page on Butterworth filters, or a textbook on digital signal processing - one (of probably many) useful applied text for seismology is Gubbins, Time Series Analysis and Inverse Theory.

Is â€ścornerâ€ť synonymous to â€śorderâ€ť of the filter here? My confusion is that, being not a signal-processing expert, the sources I read, including the two you pointed out, do not use the word â€ścornerâ€ť but instead they talk about the â€śorderâ€ť. My understanding is that these are the same? For example, the figure here (from Gubbins) shows corners = 1, 2, 4, 6 and essentially higher â€ścornerâ€ť number means sharper roll-off, and the filtered data should eventually stop changing at some value of â€ścornerâ€ť .

Just want to confirm if my understanding is correct.

Exactly, â€ścornersâ€ť is synonymous to â€śorderâ€ť of the filter. Only for `zerophase=True`

the final filter order is twice the value of `corners`

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