Description
Writing multi-lagged inputs to Scan is not very intuitive. You pass a dictionary with outputs_info={"initial": var, "taps": [-2, -1]}. I don't usually remember the name of the keys, and also I don't think taps is a great name.
Syntatic-sugar suggestion, offer a function lags?
outputs_info=scan.lags(var, n=2) that creates the dict? Docstrings can be used to provide useful info for the user: What are lagged inputs, how a minimal step function may look like, what the input order is in the inner function (-2, -1), not (-1, -2), etc....
We can also call it scan.taps or something else. The main idea is having a function for discoverability / auto-completion
Next-level suggestion
If the user uses the lags constructor, the user function doesn't receive separate lagged arguments but a tuple of them?
def step(seq_val, lagged_var, constant):
xtm2, xtm1 = lagged_var
GPT-5 explanation for the term taps:
Origin: “Taps” comes from signal processing. In FIR/IIR filters you read from a delay line at different “taps” (connection points) to access delayed samples; scan borrowed that for relative time-step reads.
GPT-5 name alternative suggestions:
Short answer
Better name: index_offsets (most general/clear), with time_offsets or lags as good alternates depending on audience.
Details
Why index_offsets: Scan iterates along an axis; the parameter is a set of relative indices w.r.t. the current step (e.g., [-2, -1, 0, +1]). “Index offsets” is precise, axis-agnostic, and conveys sign.
Other viable names (trade-offs):
- time_offsets: very readable for time series; slightly misleading if the axis isn’t time.
- lags: common in statistics; intuitive for negatives, less so for positives (often called “leads”).
- delays: DSP-friendly; similar ambiguity for positive offsets.
- relative_steps: explicit but longer.
- lookback_steps: only fits negative offsets.
Description
Writing multi-lagged inputs to Scan is not very intuitive. You pass a dictionary with
outputs_info={"initial": var, "taps": [-2, -1]}. I don't usually remember the name of the keys, and also I don't thinktapsis a great name.Syntatic-sugar suggestion, offer a function
lags?outputs_info=scan.lags(var, n=2)that creates the dict? Docstrings can be used to provide useful info for the user: What are lagged inputs, how a minimal step function may look like, what the input order is in the inner function (-2, -1), not (-1, -2), etc....We can also call it
scan.tapsor something else. The main idea is having a function for discoverability / auto-completionNext-level suggestion
If the user uses the lags constructor, the user function doesn't receive separate lagged arguments but a tuple of them?
GPT-5 explanation for the term taps:
Origin: “Taps” comes from signal processing. In FIR/IIR filters you read from a delay line at different “taps” (connection points) to access delayed samples; scan borrowed that for relative time-step reads.
GPT-5 name alternative suggestions:
Short answer
Better name: index_offsets (most general/clear), with time_offsets or lags as good alternates depending on audience.
Details
Why index_offsets: Scan iterates along an axis; the parameter is a set of relative indices w.r.t. the current step (e.g., [-2, -1, 0, +1]). “Index offsets” is precise, axis-agnostic, and conveys sign.
Other viable names (trade-offs):