# Function apply Apply a function that maps an array to a scalar along a given axis of a matrix or array. Returns a new matrix or array with one less dimension than the input. ## Syntax ```js math.apply(A, dim, callback) ``` ### Where - `dim: number` is a zero-based dimension over which to concatenate the matrices. ### Parameters Parameter | Type | Description --------- | ---- | ----------- `array` | Array | Matrix | The input Matrix `dim` | number | The dimension along which the callback is applied `callback` | Function | The callback function that is applied. This Function should take an array or 1-d matrix as an input and return a number. ### Returns Type | Description ---- | ----------- Array | Matrix | res The residual matrix with the function applied over some dimension. ## Examples ```js const A = [[1, 2], [3, 4]] const sum = math.sum math.apply(A, 0, sum) // returns [4, 6] math.apply(A, 1, sum) // returns [3, 7] ``` ## See also [map](map.md), [filter](filter.md), [forEach](forEach.md)