josdejong/mathjs

Matrix sum along a dimension is defined to return a `MathScalarType`, but might return higher dimension

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#3,202 opened on May 12, 2024

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 (5 comments) (0 reactions) (1 assignee)JavaScript (13,832 stars) (1,298 forks)batch import
bughelp wantedtypescript

Description

Describe the bug When summing over an axis of a matrix, we always lose just one dimension. If the matrix is 2D, we'll get a 1D array. If the matrix is 3D, we'll get a 2D matrix. What happens now, is that math.sum declares that it returns a MathScalarType, instead of optionally returning a matrix.

To Reproduce

const mat = math.matrix([[1,2,3],[4,5,6]])
console.log(math.sum(mat, 0))

> DenseMatrix { _data: [ 5, 7, 9 ], _size: [ 3 ], _datatype: undefined }

Contributor guide

Tech stack
javascript
Domain
api
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
blocked
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Basic JavaScript knowledgeUnderstanding of matrix operationsFamiliarity with math.js types
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50
Research direction
The bug is in the type signature of the sum function in mathjs. The issue likely requires updating the return type in the TypeScript declaration file (if any) or the JSDoc comment in the source file (e.g., src/type/matrix/function/sum.js). The code currently returns the result of math.sum which may be a DenseMatrix instead of a scalar. To fix, the function should return a MathGenericType or similar that accounts for multidimensional arrays. The existing tests in the test directory may need to be updated to cover this case. No linked PRs yet; the assignee may be working on a fix.