Outer product

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
52/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Stale
Tech stack
rust
Domain
data

Research direction

Start by locating ArrayBase's existing dot and reshape APIs and the implementation of similar array operations. Add the proposed one-dimensional outer-product API, then add coverage for the shown vectors and confirm that the resulting two-dimensional values match the expected outer product.

Written by the indexing model from the issue text.

Description

I found that ArrayBase has no equivalent method to np.outer of numpy. This is quite surprising because outer product is a standard feature and is trivial to implement.

For example, by refering to the implementation of np.outer, we can implement ArrayBase's outer as:

pub fn outer(x: &Array<f64, Ix1>, y: &Array<f64, Ix1>) -> Array<f64, Ix2> {
    let (size_x, size_y) = (x.shape()[0], y.shape()[0]);
    let x_reshaped = x.view().into_shape((size_x, 1)).unwrap();
    let y_reshaped = y.view().into_shape((1, size_y)).unwrap();
    x_reshaped.dot(&y_reshaped)
}

then

let a = array![1., 2., 3.];
let b = array![1., 2., 3.];

let outer = a.outer(&b);

There is a similar issue/pull request #690, but it implements Kronecker product not outer.

Dominant language
Rust
Stars
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Forks
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