Math.NET Numerics - Matrix from an array of doubles

Question

Assuming I have:

double[] someArray = new [] { 11, 12, 13, 14, 21, 22, 23, 24, 31, 32, 33, 34, 41, 42, 43, 44 };

Is there any out of the box way of creating a 4x4 matrix out of this array without having to split it into 4 arrays myself?

I know it is simple to do this, but I'm exploring how much is ready out of the box.

EDIT

Sorry for not being clear (thought title was):

What I'm wondering is if there is out of the box functionality with the Matrix builder in Math.NET Numerics. Something like:

Matrix<double> someMatrix = DenseMatrix.OfArray(columns: 4, rows: 4, data: someArray);

How do values in this array correspond to matrix values? Math.NET Numerics dense matrices use column-major order internally, but other libraries may use row-major or something else completely. — Christoph Rüegg, Oct 07 '14 at 15:22

Meta-Knight · Accepted Answer · 2014-10-07T15:31:50.397

5

From looking at the documentation, you could use the constructor directly, or the function OfColumnMajor(int rows, int columns, IEnumerable<double> columnMajor), if your data is in column-major order.

The code would look like this:

//Using the constructor
Matrix<double> someMatrix = new DenseMatrix(4, 4, someArray)

//Using the static function
Matrix<double> someMatrix = DenseMatrix.OfColumnMajor(4, 4, someArray);

If your data is in row-major order, you could split into arrays and use one of the OfRows function, or use the constructor and transpose the matrix, as suggested by Christoph.

edited Oct 07 '14 at 15:31

answered Oct 07 '14 at 15:11

Meta-Knight

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Yes, provided the array is in column-major order. – Christoph Rüegg Oct 07 '14 at 15:19
Yes, otherwise there is no OfRowMajor function, you would have to split into arrays and use OfRows function. – Meta-Knight Oct 07 '14 at 15:21
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NB: if the data is in column-major order you can also use the [constructor](http://numerics.mathdotnet.com/api/MathNet.Numerics.LinearAlgebra.Double/DenseMatrix.htm#.ctor) directly. This is in fact the most efficient way to create a dense matrix. – Christoph Rüegg Oct 07 '14 at 15:23
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In case of row-major you can still use the constructor (with switched cols/rows dimensions) and then transpose the resulting matrix. – Christoph Rüegg Oct 07 '14 at 15:25
@ChristophRüegg Thanks for providing with the useful extra info. It was my next question (row-major scenarios) – johnildergleidisson Oct 07 '14 at 15:40

Math.NET Numerics - Matrix from an array of doubles

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