I need to inverse a matrix given in a file. The problem is I'm stuck with writing determinant finding algoritm into code. I found this algoritm about finding determinant of nxn matrix. This is what i need: http://www.maths.surrey.ac.uk/explo... and here: a11 a12 a13 a21 a22 a23 a31 a32 a33  = a11(a22a33 − a23a32) − a12(a21a33 − a23a31) + a13(a21a32 − a22a31) Note the pattern of + and − signs. The general formula is compact, but tedious to compute. Here it is for an n by n matrix A: detA = ai1Ci1 + ai2Ci2 + · · · + ainCin where Cij are referred to as the cofactors and are computed from Cij = (−1)i+j detMij The term Mij is known as the ”minor matrix” and is the matrix you get if you eliminate row i and column j from matrix A. So to find the determinant of e.g. a 4×4 matrix, you end up calculating a bunch of 3 × 3 matrix determinants (much easier). Obviously you can apply this technique recursively (probably using a computer). *************** Can some1 please write it into my code or if he has time even complete the full inverse. I read the matrix from a file into an array "row": ---------------- #!/usr/bin/awk -f BEGIN{} { m=1 while (m <= NF){ row[NR,m] = $m m++ } } END{} -------------- thank you.

I got something done, but it only works for 2*2 and 3*3 matrices. There must be a mistake. I used the code I found somewhere: int determinant(int b[5][5],int m) //FUNCTION TO CALCULATE DETERMINANT { int i,j,sum = 0,c[5][5]; if(m==2) { //BASE CONDITION sum = b[0][0]*b[1][1] - b[0][1]*b[1][0]; return sum; } for(int p=0;p<m;p++) { int h = 0,k = 0; for(i=1;i<m;i++) { for( j=0;j<m;j++) { if(j==p) continue; c[h][k] = b[i][j]; k++; if(k == m-1) { h++; k = 0; } } } sum = sum + b[0][p]*pow(-1,p)*determinant(c,m-1); } return sum; } I also used this: function det( a, n ) if n = 2 then d := a11·a22 - a12·a21 else d := 0 for i := 1...n do M1i <-- A with row 1 and column i deleted d := d + (-1)(i-1)·a1i·det( M1i, n - 1 ) end for end if return d end function And got my awk code: function det(a, n) { if (n == 2) { d = a[1,1] * a[2,2] - a[1,2] * a[2,1] print d } else { d=0 for(i = 1; i <= n; i++){ k=1 j=1 for (x = 2; x <= n; x++) { for (z = 1; z <= n; z++){ if (z==i) {z++} M[k,j]= a[x,z] j++} j=1 k++ } d= d + miinus1_astmel(i-1)*a[1,i]*det( M, n - 1) } return d } function miinus1_astmel(n){ vastus=1 for (x=1; x<=n; x++){ vastus=vastus*(-1) } return vastus } Looks the same to me, but somewhere is a mistake.