Roll array along an axis

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Stale
Tech stack
numpy, rust
Domain
data

Research direction

Start by reviewing the crate's existing array-axis and view/indexing APIs, using the np.roll examples as the behavioral reference. Determine how rolling by an axis and signed shift should behave, including wraparound and the central-difference example. Done means the crate exposes equivalent rolling behavior with coverage for the shown two-dimensional cases.

Written by the indexing model from the issue text.

Description

In numpy you can roll an array along an axis. Which is an index shift with wrap around, meaning, that given an array

a = np.arange(1, 10).reshape(3, 3)
[[1, 2, 3],
 [4, 5, 6],
 [7, 8, 9]]

rolling along the 2nd axis by 1 results in

np.roll(a, 1, 1)
[[3, 1, 2],
 [6, 4, 5],
 [9, 7, 8]]

I wonder if this can be cheaply implemented in this crate, since it is basically just a remapping of indices? It would be useful to calculate a gradient with periodic boundaries (wrap around). For example, a central difference (modulo prefactors) in y direction can be implemented like

np.roll(a, -1, 1) - np.roll(a, 1, 1)
[[-1,  2, -1],
 [-1,  2, -1],
 [-1,  2, -1]
Dominant language
Rust
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Forks
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