Re: rank question

[Tatsuro MATSUOKA]

> From: Tatsuro MATSUOKA 

> To: "help-octave
> Cc: 
> Date: 2016/6/4, Sat 10:10
> Subject: rank question
> 
> Hello
> 
> Perhaps I have mislead
> 
>>>  A=[
> 1,2,3,4,5,6,7
> 7,6,5,4,3,2,1
> 9,10,11,12,13,14,16
> 6,4,2,0,-2,-4,6
> 10,12,14,16,18,20,22
> ]
> A =
> 
>     1    2    3    4    5    6    7
>     7    6    5    4    3    2    1
>     9   10   11   12   13   14   16
>     6    4    2    0   -2   -4    6
>    10   12   14   16   18   20   22
> 
>>>  rank(A)
> ans =  3
> The same results  are obtained on Scilab and Maxima.
> 
> However, row basic deformations of A give to 
> 
>     1    2    3    4    5    6    7
>     0   -8  -16  -24  -32  -40  -48
>     0   -8  -16  -24  -32  -40  -48
>     0   -8  -16  -24  -32  -40  -48
>     0   -8  -16  -24  -32  -40  -48
> 
>     1    2    3    4    5    6    7
>     0    1    2    3    4    5    6
>     0    0    0    0    0    0    0
>     0    0    0    0    0    0    0
>     0    0    0    0    0    0    0
> 
> Is not the rank of A two (2)?
> Am I misled ?
> 
> Tatsuro


Sorry for my typo.

>> A=[
1,2,3,4,5,6,7
7,6,5,4,3,2,1
9,10,11,12,13,14,15
6,4,2,0,-2,-4,6
10,12,14,16,18,20,22
]
A =

    1    2    3    4    5    6    7
    7    6    5    4    3    2    1
    9   10   11   12   13   14   15
    6    4    2    0   -2   -4    6
   10   12   14   16   18   20   22

>> rank(A)
ans =  3

is correct.
For the first post,
Row basic deformations of A give to 
 
     1    2    3    4    5    6    7
     0   -8  -16  -24  -32  -40  -48
     0   -8  -16  -24  -32  -40  -47
     0   -8  -16  -24  -32  -40  -48
     0   -8  -16  -24  -32  -40  -48
 
     1    2    3    4    5    6    7
     0    1    2    3    4    5    6
     0    0    0    0    0    0    1
     0    0    0    0    0    0    0
     0    0    0    0    0    0    0


ans rank(A) is surely 3.

Tatsuro