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PORecursive function for matrix determinant calculator
 

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  1. PORecursive function for matrix determinant calculator
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    <p>I am playing with arrays and I try to make a recursive function to calculate the determinant of a matrix A[i][j], where i=j=k. The function that I wrote is as follows. It seems that I am doing something wrong but I can't tell what. The A array is defined by user and read by another function. I try to do it without using and libraries or predefined objects. I have added the whole code as for you to make a general idea:</p> <pre><code>&lt;script&gt; var k; function readGrad() { //reads the matrix dimesnions k = parseInt(document.getElementById("grad").value); if (isNaN(k)) { alert('Gradul introdus nu este intreg, reintroduceti gradul matricii'); } if (k == 0) { alert ('Determinantul trebuie sa fie mai mare ca 1'); } if (k == 1) { alert ('Determinantul trebuie sa fie mai mare ca 1'); } return k; } function genTable(i,j) { //generates the table for the user to insert the values //var i,j = parseInt(document.getElementById("grad").value); var myTable = '&lt;TABLE BORDER="1" BORDERCOLOR="BLACK"&gt;\n &lt;TBODY&gt;\n'; for (i = 0; i &lt; 1; i++) { myTable += ' &lt;TR&gt;\n'; for (j = 0; j &lt; k+1; j++) { myTable += ' &lt;TD&gt;'+j+'&lt;/TD&gt;\n'; } myTable += ' &lt;/TR&gt;\n'; } for (i = 1; i &lt; k+1; i++) { myTable += ' &lt;TR&gt;\n'; for (j = 0; j &lt; 1; j++) { myTable += ' &lt;TD&gt;'+i+'&lt;/TD&gt;\n'; } for (j = 1; j &lt; k+1; j++) { myTable += ' &lt;TD&gt;&lt;input class="element" id="A' + i + j + '"value="0"&gt;&lt;/TD&gt;\n'; } myTable += ' &lt;/TR&gt;\n'; } myTable += ' &lt;/TBODY&gt;\n&lt;/TABLE&gt;\n'; document.getElementById('container').innerHTML = myTable; } function calcDet () { var A = []; //generates the array for (var i = 0; i &lt; k; i++) { A[i] = []; for (var j = 0; j &lt; k; j++) { A[i][j] = i + ':' + j; } } for (var i = 0; i &lt; k; i++) { //reads the array for (var j=0; j&lt;k; j++) { var id = "A" + (i + 1) + (j + 1); A[i][j] = parseFloat(document.getElementById(id).value); } } var s; var det = 0; function calcRec (A) { if (A.length == 1) { //bottom case of the recursive function alert (A) } if (i == 2) { det = A[0][0] * A[1][1] - A[1][0] * A [0][1]; alert (det); } for (var i=0; i&lt;k; i++) { //creates smaller matrix- values not in same row, column var smaller=new Array(A.length-1); for(h=0;h&lt;smaller.length;h++){ smaller[h]=new Array(smaller.length); } } for(a=1;a&lt;A.length;a++){ for(b=0;b&lt;A.length;b++){ if(b&lt;i){ smaller[a-1][b]=A[a][b]; } else if(b&gt;i){ smaller[a-1][b-1]=A[a][b]; } } } if (i%2==0) { s=1; } else { s=-1; } det+=s*matrix[0][i]*(calcRec(smaller)); return (det); } } &lt;/script&gt; &lt;body style="background-color: #777; color: ddd;"&gt; &lt;div style="margin: 20px;"&gt; &lt;h1&gt;Program de calculare determinant matrice de orice grad.&lt;/h1&gt; &lt;/div&gt; &lt;div&gt; Introduceti gradul matricei &lt;input id="grad" type="text" value="" style="width: 50px;" onChange="readGrad()"&gt; &lt;input style="margin-top: 20px;" type="button" name="Calculate determinant" value="Generati tabel" onClick="genTable()"&gt; &lt;/div&gt; &lt;form name="Det Matrice"&gt; &lt;div style="margin-top: 100px; float: left; width: 100%;"&gt; Introduceti valorile: &lt;table style="text-align: center;"&gt; &lt;div id="container"&gt;&lt;/div&gt; &lt;/table&gt; &lt;br&gt; &lt;/div&gt; &lt;div style="float: left; margin-top: 20px;"&gt; &lt;input type="button" name="Calculate determinant" value="Calculati determinant" onClick="calcDet()"&gt; &lt;/div&gt; &lt;/form&gt; &lt;/body&gt; </code></pre>
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    1. COCan you give some more detail about what goes wrong? Is any error being thrown? Some example input, expected output, and the 'wrong' output you get would also help.
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    2. COthe ideea is that when I press a button the calcDet() is called and it should alert the final value of the det, however now nothing happens. the code is rather lengthy. I can add it if you want, but everything works out just fine if I comment out this function and replace it with a simple alert(A).
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      1. USviktor
    3. COI have added the whole code
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      1. USviktor
 

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