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).







I

n


=


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1


0


0


⋯


0




0


1


0


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0




0


0


1


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0




⋮


⋮


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⋱


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0


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1



]




{\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)


 
function identity($length) {
	return array_map(function($key, $value) {$value[$key] = 1; return $value;}, range(0, $length-1),
	array_fill(0, $length, array_fill(0,$length, 0)));
}
function print_identity($identity) {
	echo implode(PHP_EOL, array_map(function ($value) {return implode(' ', $value);}, $identity));
}
print_identity(identity(10));
 