Task

Build an   identity matrix   of a size known at run-time.



An identity matrix is a square matrix of size n × n,

where the diagonal elements are all 1s (ones),

and all the other elements are all 0s (zeroes).







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{\displaystyle I_{n}={\begin{bmatrix}1&0&0&\cdots &0\\0&1&0&\cdots &0\\0&0&1&\cdots &0\\\vdots &\vdots &\vdots &\ddots &\vdots \\0&0&0&\cdots &1\\\end{bmatrix}}}





Related tasks

   Spiral matrix
   Zig-zag matrix 
   Ulam_spiral_(for_primes)


/* Identity matrix, in Jsish */
function identityMatrix(n) {
    var mat = new Array(n).fill(0);
    for (var r in mat) {
        mat[r] = new Array(n).fill(0);
        mat[r][r] = 1;
    }
    return mat;
}
 
provide('identityMatrix', 1);
 
if (Interp.conf('unitTest')) {
;    identityMatrix(0);
;    identityMatrix(1);
;    identityMatrix(2);
;    identityMatrix(3);
    var mat = identityMatrix(4);
    for (var r in mat) puts(mat[r]);
}
 
/*
=!EXPECTSTART!=
identityMatrix(0) ==> []
identityMatrix(1) ==> [ [ 1 ] ]
identityMatrix(2) ==> [ [ 1, 0 ], [ 0, 1 ] ]
identityMatrix(3) ==> [ [ 1, 0, 0 ], [ 0, 1, 0 ], [ 0, 0, 1 ] ]
[ 1, 0, 0, 0 ]
[ 0, 1, 0, 0 ]
[ 0, 0, 1, 0 ]
[ 0, 0, 0, 1 ]
=!EXPECTEND!=
*/