A_inverse*A=Identity Matrix in Octave? -

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this question has answer here:

if nxn matrix, in octave, pinv(a) represent inverse of a. pinv(a)*a should yield identity matrix i(n). following code not working.

a=[ 1 2 3, 4 5 6, 7 8 9];  pinv(a)*a   0.83333   0.33333  -0.16667 0.33333   0.33333   0.33333 -0.16667   0.33333   0.83333

the diagonal elements , (pinv(a)*(a))[i,i] i=1,2,3 not near one.what went wrong?

try use inv(a) function , useful information:

 >> inv(a)  warning: matrix singular machine precision, rcond = 1.54198e-018

matrix not invertible! singular. try change matrix a:

>> a=[ 10 2 3; 4 5 6; 7 8 9] = 10    2    3 4    5    6 7    8    9 >> inv(a)*a ans =  1.00000   0.00000   0.00000 -0.00000   1.00000   0.00000  0.00000   0.00000   1.00000 >> pinv(a)*a ans =  1.0000e+000  -2.2204e-016  -4.4409e-016 -1.7764e-015  1.0000e+000  -3.5527e-015  5.3291e-015  5.3291e-015  1.0000e+000

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