# multidim-array-index

maps multidimensional array indices to monodimensional array index

## Installation

With npm do

``````npm install multidim-array-index
``````

## Examples

All code in the examples below is intended to be contained into a single file.

``````var multiDimArrayIndex = require('multidim-array-index')
``````

### 1th-order

In the monodimensional case, it just returns the index itself.

``````var i3 = multiDimArrayIndex.bind(null, [3])

i3([0]) // 0
i3([1]) // 1
i3([2]) // 2
``````

### 2th-order

For a two dimensional case, for instance a matrix, it is equivalent to the function `(i, j, numCols) => j + i * numCols`

``````var i2x3 = multiDimArrayIndex.bind(null, [2, 3])

i2x3([0, 0]) // 0
i2x3([0, 1]) // 1
i2x3([0, 2]) // 2
i2x3([1, 0]) // 3
i2x3([1, 1]) // 4
i2x3([1, 2]) // 5
``````

### 3th-order

``````var i2x3x4 = multiDimArrayIndex.bind(null, [2, 2, 2])

i2x3x4([0, 0, 0]) // 0
i2x3x4([0, 0, 1]) // 1
i2x3x4([0, 0, 2]) // 2
i2x3x4([0, 0, 3]) // 3
i2x3x4([0, 1, 0]) // 4
i2x3x4([0, 1, 1]) // 5
i2x3x4([0, 1, 2]) // 6
i2x3x4([0, 1, 3]) // 7
i2x3x4([1, 0, 0]) // 8
i2x3x4([1, 0, 1]) // 9
i2x3x4([1, 0, 2]) // 10
i2x3x4([1, 0, 3]) // 11
i2x3x4([1, 1, 0]) // 12
i2x3x4([1, 1, 1]) // 13
i2x3x4([1, 1, 2]) // 14
i2x3x4([1, 1, 3]) // 15

i2x2x2([0, 0, 0]) //// 0
i2x2x2([0, 0, 1]) // 1
i2x2x2([0, 1, 0]) // 2
i2x2x2([0, 1, 1]) // 3
i2x2x2([1, 0, 0]) // 4
i2x2x2([1, 0, 1]) // 5
i2x2x2([1, 1, 0]) // 6
i2x2x2([1, 1, 1]) // 7
``````

## API

### `multiDimArrayIndex(dimension, indices)`

• @param `{Array}` dimensions defines the shape of the multi dimensional array
• @param `{Array}` indices to transform
• @returns `{Number}` index of an equivalent mono dimensional array

Given dimensions `d_1, d_2, d_3 .. d_n` and indices `i_1, i_2, i_3 .. i_n` index is computed by formula

``````index = i_n + i_(n-1) * d_n + i_(n-2) * d_n * d_(n-1) + ... + i_2 * d_n * d_(n-1) * ... * d_3 + i_1 * d_n * ... * d_2
``````

### `multiDimArrayIndex.error`

An object exposing the following error messages:

• outOfBoundIndex

For example, the following snippets will throw

``````// outOfBoundIndex

i3([11])
i2x3x4([2, 3, 5])
``````