Open liamtoney opened 1 year ago
In the Causal versus acausal section of the notebook, there looks to be a typo where the "causal" filters have
zerophase=True
while the "acausal" filter haszerophase=False
.
I agree, that looks like an error in there. The wording is also weird: "The output of a causal filter depends only on past and present input, while the output also depends on future input."
The second half of the sentence is about acausal filter only mentioned in the following sentence. It probably should be ..., while the output [of an acausal filter] also depends on future input.
"causal" and "acausal" would need to be swapped here — the trace in green has a phase shift due to its causal nature, not the opposite.
Agreed.
It is my understanding that the final two sentences here are correct, but in this case for the wrong reason.
I guess the wording could be improved but in general it seems OK like you said.
It would be good to have these things fixed. Sadly, currently we don't have a set workflow for making updates to seismo live, so it means quite some work, so not sure how/when an update would make it to the live webpage.
CC @heinerigel
Thanks for these great resources.
I was trying to understand causal / acausal filtering today in the context of ObsPy's functions and came across the Basics in filtering notebook.
In the Causal versus acausal section of the notebook, there looks to be a typo where the "causal" filters have
zerophase=True
while the "acausal" filter haszerophase=False
.Presumably, these should be switched?
On a related note, in the solutions the following discussion:
"causal" and "acausal" would need to be swapped here — the trace in green has a phase shift due to its causal nature, not the opposite.
It is my understanding that the final two sentences here are correct, but in this case for the wrong reason. The causal filter does introduce a phase shift but it is typically used in phase picking applications to avoid pre-onset artifacts arising from acausal filtering of impulsive arrivals, correct? It might be good to clarify here.
I would be happy to draft a quick PR to address these comments, if they make sense to the notebook creators.