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POCo Factor of a Matrix in Java (used to determine the inverse of a matrix)
 

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    <p>I am trying to determine the inverse of a matrix using the adjoint method i.e. (First calculate the cofactor of the matrix, then transpose this matrix and finally, multiply it by (1/determinant) for the inverse of the value of the determinant) I have methods that determine the transpose and determinant, however i am struggling with the cofactor matrix -</p> <p>Link showing how the inverse is determined using the adjoint method by hand <a href="http://www.mathwords.com/i/inverse_of_a_matrix.htm" rel="nofollow">http://www.mathwords.com/i/inverse_of_a_matrix.htm</a> Link showing how the cofactor is calculated by hand <a href="http://www.mathwords.com/c/cofactor_matrix.htm" rel="nofollow">http://www.mathwords.com/c/cofactor_matrix.htm</a>></p> <p>I have a method that calculates the determinant and the transpose fine, but I cant get the cofactor method to give me the output I require</p> <p>A sample output is => 24 5 -4<br> 24 5 -4<br> 24 5 -4 but the second &amp; third row should be different, any suggestions? Thanks! Here is the method that I am using => The checkIfSquare and assigningSign methods are working fine also </p> <pre><code> public static int[][] cofactor(int[][] matrix) { int[][] cofactorMatrix = new int[matrix.length][matrix.length]; for (int j = 0; j &lt; matrix.length; j++) { if (checkIfSquare(matrix)) { for (int location = 0; location &lt; matrix.length; location++) { int reducedMatrix[][] = new int[matrix.length - 1][matrix.length - 1]; for (int rows = 1; rows &lt; matrix.length; rows++) { for (int cols = 0; cols &lt; matrix.length; cols++) { if (cols &gt; location) { reducedMatrix[rows - 1][cols - 1] = matrix[rows][cols]; } else if (cols &lt; location) { reducedMatrix[rows - 1][cols] = matrix[rows][cols]; } } } int sign = assigningSign(location); cofactorMatrix[j][location] = determinantCalc(reducedMatrix) * sign; } } } return cofactorMatrix; } </code></pre>
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