# Make a matrix from an Array?

Posted 2 months ago
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 I have this code: n=Input[]; Array[mat,{n,n}]; For[i = 1, i < n+1, i++, For[j = 1, j < n+1, j++, mat[i,j]=0; ] ] d=Det[mat]; Print[d]; And when I input "2", the result is 1, which can't be true. Is there something with an Array being a matrix? Answer
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Posted 2 months ago
 Your mat is the head of the array. The array itself is Array[mat,{n,n}]: n = Input[]; myArray = Array[mat, {n, n}]; For[i = 1, i < n + 1, i++, For[j = 1, j < n + 1, j++, mat[i, j] = 0;]] d = Det[myArray] Answer
Posted 2 months ago
 If I understand what you're trying to accomplish, which is to create a square zero-matrix, then the following does what you want:  n = Input[]; mat = ConstantArray[0, {n, n}]; Det[mat] (* 0 *) There's no earthly reason to use a Fortran-like (or Matlab-like) do loop.Moreover, if you're filling the matrix with 0's, you would surely already know its determinant will be 0, Answer
Posted 2 months ago
 d_j^n2=Input [{n,d_d} ]; array=[mat,{n,n_d^d}]; For[i = 1, i < n+1, i++, For[j = 1, j < n+1, j++, mat[i,j]=0; ] ] d=Det[mat,{n,n}]; Print[d];    Attachments: Answer