---
name: "sgebak"
section: "3lapack"
platform: "linux"
package: "liblapack-doc"
version: "3.2.1-8"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/sgebak/3lapack"
---

# sgebak(3lapack)

forms the right or left eigenvectors of a real general matrix by backward transformation on the computed eigenvectors of the balanced matrix output by SGEBAL

## NAME

SGEBAK - forms the right or left eigenvectors of a real general matrix by backward transformation on the computed eigenvectors of the balanced matrix output by SGEBAL

## SYNOPSIS

- SUBROUTINE SGEBAK(

  JOB, SIDE, N, ILO, IHI, SCALE, M, V, LDV, INFO )

- CHARACTER

  JOB, SIDE

- INTEGER

  IHI, ILO, INFO, LDV, M, N

- REAL

  V( LDV, \* ), SCALE( \* )

## PURPOSE

SGEBAK forms the right or left eigenvectors of a real general matrix by backward transformation on the computed eigenvectors of the balanced matrix output by SGEBAL.

## ARGUMENTS

- JOB (input) CHARACTER\*1

  Specifies the type of backward transformation required: = 'N', do nothing, return immediately; = 'P', do backward transformation 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 SGEBAL.

- 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 SGEBAL. 1 \<= ILO \<= IHI \<= N, if N \> 0; ILO=1 and IHI=0, if N=0.

- SCALE (input) REAL array, dimension (N)

  Details of the permutation and scaling factors, as returned by SGEBAL.

- M (input) INTEGER

  The number of columns of the matrix V.  M \>= 0.

- V (input/output) REAL array, dimension (LDV,M)

  On entry, the matrix of right or left eigenvectors to be transformed, as returned by SHSEIN or STREVC. On exit, V is overwritten 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.