I'm trying to convert this function from Jagged Array to 2D array, and I'm not able to convert everything Original Function:
public static double[][] InvertMatrix(double[][] A)
{
int n = A.Length;
//e will represent each column in the identity matrix
double[] e;
//x will hold the inverse matrix to be returned
double[][] x = new double[n][];
for (int i = 0; i < n; i++)
{
x[i] = new double[A[i].Length];
}
/*
* solve will contain the vector solution for the LUP decomposition as we solve
* for each vector of x. We will combine the solutions into the double[][] array x.
* */
double[] solve;
//Get the LU matrix and P matrix (as an array)
Tuple<double[][], int[]> results = LUPDecomposition(A);
double[][] LU = results.Item1;
int[] P = results.Item2;
/*
* Solve AX = e for each column ei of the identity matrix using LUP decomposition
* */
for (int i = 0; i < n; i++)
{
e = new double[A[i].Length];
e[i] = 1;
solve = LUPSolve(LU, P, e);
for (int j = 0; j < solve.Length; j++)
{
x[j][i] = solve[j];
}
}
return x;
}
What I have converted until now:
public static double[,] InvertMatrix(double[,] A)
{
int n = A.Length;
//e will represent each column in the identity matrix
double[] e;
//x will hold the inverse matrix to be returned
double[,] x = new double[n][];
for (int i = 0; i < n; i++)
{
//how to convert this line?
x[i] = new double[A[i].Length];
}
/*
* solve will contain the vector solution for the LUP decomposition as we solve
* for each vector of x. We will combine the solutions into the double[][] array x.
* */
double[] solve;
//Get the LU matrix and P matrix (as an array)
Tuple<double[,], int[]> results = LUPDecomposition(A);
double[,] LU = results.Item1;
int[] P = results.Item2;
/*
* Solve AX = e for each column ei of the identity matrix using LUP decomposition
* */
for (int i = 0; i < n; i++)
{
//This one too?!
e = new double[A[i].Length];
e[i] = 1;
solve = LUPSolve(LU, P, e);
for (int j = 0; j < solve.Length; j++)
{
x[j,i] = solve[i,j];
}
}
return x;
}
How to convert x[i] = new double[A[i].Length] to 2D array?
This snippet can be helpful
static T[,] To2D<T>(T[][] source)
{
try
{
int FirstDim = source.Length;
int SecondDim = source.GroupBy(row => row.Length).Single().Key; // throws InvalidOperationException if source is not rectangular
var result = new T[FirstDim, SecondDim];
for (int i = 0; i < FirstDim; ++i)
for (int j = 0; j < SecondDim; ++j)
result[i, j] = source[i][j];
return result;
}
catch (InvalidOperationException)
{
throw new InvalidOperationException("The given jagged array is not rectangular.");
}
}
Usage:
double[][] array = { new double[] { 52, 76, 65 }, new double[] { 98, 87, 93 }, new double[] { 43, 77, 62 }, new double[] { 72, 73, 74 } };
double[,] D2 = To2D(array);
UPD: For those scenarios where unsafe context is acceptable there is a faster solution, thanks Styp: https://stackoverflow.com/a/51450057/3909293