inv

Arguments

X

real or complex square matrix, polynomial matrix, rational matrix in transfer or state-space representation.

Description

inv(X) is the inverse of the square matrix X. A warning message is printed if X is badly scaled or nearly singular.

For polynomial matrices or rational matrices in transfer representation, inv(X) is equivalent to invr(X).

inv([]) returns [].

For linear systems in state-space representation (syslin list), invr(X) is equivalent to invsyslin(X).

References

inv function for matrices of numbers is based on the Lapack routines DGETRF, DGETRI for real matrices and ZGETRF, ZGETRI for the complex case. For polynomial matrix and rational function matrix inv is based on the invr Scilab function.

Examples

A=rand(3,3);inv(A)*A

x=poly(0,'x');
A=[x,1,x;x^2,2,1+x;1,2,3];inv(A)*A

A=[1/x,2;2+x,2/(1+x)]
inv(A)*A

A=ssrand(2,2,3);
W=inv(A)*A
clean(ss2tf(W))

See also

• slash — (/) right division and feed back
• backslash — (\) left matrix division.
• pinv — pseudoinverse
• qr — QR decomposition
• lufact — sparse lu factorization
• lusolve — sparse linear system solver
• invr — inversion of (rational) matrix
• coff — resolvent (cofactor method)
• coffg — Co-factors of a matrix of polynomials or rationals