# Ubuntu Feisty 7.04 manual page repository

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### NAME

```        ZGEBAK  -  form  the  right  or  left eigenvectors of a complex general
matrix by backward transformation on the computed eigenvectors  of  the
balanced matrix output by ZGEBAL
```

### SYNOPSIS

```        SUBROUTINE ZGEBAK( JOB, SIDE, N, ILO, IHI, SCALE, M, V, LDV, INFO )

CHARACTER      JOB, SIDE

INTEGER        IHI, ILO, INFO, LDV, M, N

DOUBLE         PRECISION SCALE( * )

COMPLEX*16     V( LDV, * )
```

### PURPOSE

```        ZGEBAK forms the right or left eigenvectors of a complex general matrix
by backward transformation on the computed eigenvectors of the balanced
matrix output by ZGEBAL.
```

### ARGUMENTS

```        JOB     (input) CHARACTER*1
Specifies  the type of backward transformation required: = ’N’,
do nothing, return immediately; = ’P’, do backward  transforma‐
tion  for  permutation  only; = ’S’, do backward transformation
for scaling only; = ’B’, do backward transformations  for  both
permutation  and scaling.  JOB must be the same as the argument
JOB supplied to ZGEBAL.

SIDE    (input) CHARACTER*1
= ’R’:  V contains right eigenvectors;
= ’L’:  V contains left eigenvectors.

N       (input) INTEGER
The number of rows of the matrix V.  N >= 0.

ILO     (input) INTEGER
IHI     (input) INTEGER The integers ILO and IHI determined  by
ZGEBAL.   1  <=  ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if
N=0.

SCALE   (input) DOUBLE PRECISION array, dimension (N)
Details of the permutation and scaling factors, as returned  by
ZGEBAL.

M       (input) INTEGER
The number of columns of the matrix V.  M >= 0.

V       (input/output) COMPLEX*16 array, dimension (LDV,M)
On entry, the matrix of right or left eigenvectors to be trans‐
formed, as returned by ZHSEIN or ZTREVC.  On exit, V  is  over‐
written by the transformed eigenvectors.

LDV     (input) INTEGER
The leading dimension of the array V. LDV >= max(1,N).

INFO    (output) INTEGER
= 0:  successful exit
< 0:  if INFO = -i, the i-th argument had an illegal value.

```
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