MATLAB POLYSPACE RELEASE NOTES Manual do Utilizador descarregar pdf (Página 43)

More About Matrices and Arrays

The multiplication symbol, *, denotes the matrix multipli cation involving

inner products between rows and columns. Multiplying the transpose of a

matrix by the original matrix also produces a symmetric matrix:

A'*A

ans =

378 212 206 360

212 370 368 206

206 368 370 212

360 206 212 378

The determinant of this particular matrix happens to be zero, indicating

that the matrix is singular:

d = det(A)

The reduced row echelon form of A is not the identity:

R = rref(A)

1001

010-3

0013

0000

Since the matrix is singular, it does not have an inverse. If you try to compute

the inverse with

X = inv(A)

you will get a warning message:

Warning: Matrix is close to s ingu lar or badly scaled.

Results may be inaccurate. RCOND = 9.796086e-018.

Roundoff error has prevented the matrix inversion algorithm from detecting

exact singularity. But the value of

rcond,whichstandsforreciprocal

2-21

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