Systems of linear equations

[Guest]

Hi

Does anyone know if there are AS classes or functions to solve systems of linear equations? On the form A * x = c. A is a square matrix, x is an unknown vector, and c are constant.

In other words, a system of equations with some number of unkowns (1-5), and an equal number of equations.

[kglad · Accepted solution]

here's an implementation of gaussian elimination you can use.  there's no error checking included:

package com.kglad{

    public class Gaussian_Elimination {

        public function solveF(a:Array):Array{

            for(var pivotCol:int=0;pivotCol<a[0].length-1;pivotCol++){

                a = pivotF(a,pivotCol);

                var factor:Number;

                for(var row:int=pivotCol+1;row<a.length;row++){

                    factor = a[row][pivotCol];

                    for(var _col:int=pivotCol;_col<a[0].length;_col++){

                        a[row][_col] -= a[pivotCol][_col]*factor;

                    }

                }

            }

            return echelonF(a);

        }

        private function pivotF(a:Array,pivotCol:int):Array{

            var maxAbs:Number = 0;

            var maxRow:int;

            for(var row:int=0;row<a.length;row++){

                if(Math.abs(a[row][pivotCol])>maxAbs){

                    maxRow = row;

                    maxAbs = Math.abs(a[row][pivotCol])

                }

            }

            // swap row pivotCol with maxRow

            var tempA:Array = a[pivotCol];

            // normalize maxRow

            var max:Number = a[maxRow][pivotCol];

            for(var i:int=0;i<a[maxRow].length;i++){

                a[maxRow] /= max;

            }

            a[pivotCol] = a[maxRow];

            a[maxRow] = tempA;

            return a;

        }

        private function echelonF(a:Array):Array{

            var ans:Array = [];

            var last:int = a[0].length-1;

            for(var row:int=0;row<a.length;row++){

                var term:Number = 0;

                for(var num:int=0;num<row;num++){

                    term-=a[row][last-num-1]*ans[num];

                }

                term+=a[row][last];

                ans.push(term/a[row][last-row-1]);

            }

            return ans.reverse();

        }

    }

}