Rank of block triangular matrixRank of a lower triangular block matrixThe rank of a block matrix as a function of the rank of its submatrices.Nonsingularity of a block matrixInverse of a certain block matrixWhat is the rank of this matrixRank of the product of two full rank matricesNull space and rank of block matricesAn inequality on the rank of a block matrixRank of a block lower triangular matrixProving a matrix rank equalityFind rank for this special block matrix

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Rank of block triangular matrix


Rank of a lower triangular block matrixThe rank of a block matrix as a function of the rank of its submatrices.Nonsingularity of a block matrixInverse of a certain block matrixWhat is the rank of this matrixRank of the product of two full rank matricesNull space and rank of block matricesAn inequality on the rank of a block matrixRank of a block lower triangular matrixProving a matrix rank equalityFind rank for this special block matrix













2












$begingroup$


suppose that $C$ is full column rank matrix,
can we say that the following equality is true:



$$operatornamerankbiggl(beginbmatrix
A & 0\B & C
endbmatrixbiggr)= operatornamerankbiggl(beginbmatrix
A \B
endbmatrixbiggr) +operatornamerank(C)$$



I have an idea about it:



$$beginbmatrix
A & 0\B & C
endbmatrix=beginbmatrix
A & 0\B & 0
endbmatrix+beginbmatrix
0 & 0\0 & C
endbmatrix$$
.



Now using the inequality, $textrank(A+B)leq textrank(A)+textrank(B)$ results in



$$operatornamerankbiggl(beginbmatrix
A & 0\B & C
endbmatrixbiggr)leq operatornamerankbiggl(beginbmatrix
A \B
endbmatrixbiggr) +operatornamerank(C).$$



The equality holds whenever $Rleft(beginbmatrix
A \B
endbmatrixright) cap R(C)=0$
and $Cleft(beginbmatrix
A \B
endbmatrixright) cap C(C)=0$
.



But how to conclude it in this case?!










share|cite|improve this question











$endgroup$











  • $begingroup$
    See this
    $endgroup$
    – user376343
    Sep 17 '18 at 14:55















2












$begingroup$


suppose that $C$ is full column rank matrix,
can we say that the following equality is true:



$$operatornamerankbiggl(beginbmatrix
A & 0\B & C
endbmatrixbiggr)= operatornamerankbiggl(beginbmatrix
A \B
endbmatrixbiggr) +operatornamerank(C)$$



I have an idea about it:



$$beginbmatrix
A & 0\B & C
endbmatrix=beginbmatrix
A & 0\B & 0
endbmatrix+beginbmatrix
0 & 0\0 & C
endbmatrix$$
.



Now using the inequality, $textrank(A+B)leq textrank(A)+textrank(B)$ results in



$$operatornamerankbiggl(beginbmatrix
A & 0\B & C
endbmatrixbiggr)leq operatornamerankbiggl(beginbmatrix
A \B
endbmatrixbiggr) +operatornamerank(C).$$



The equality holds whenever $Rleft(beginbmatrix
A \B
endbmatrixright) cap R(C)=0$
and $Cleft(beginbmatrix
A \B
endbmatrixright) cap C(C)=0$
.



But how to conclude it in this case?!










share|cite|improve this question











$endgroup$











  • $begingroup$
    See this
    $endgroup$
    – user376343
    Sep 17 '18 at 14:55













2












2








2





$begingroup$


suppose that $C$ is full column rank matrix,
can we say that the following equality is true:



$$operatornamerankbiggl(beginbmatrix
A & 0\B & C
endbmatrixbiggr)= operatornamerankbiggl(beginbmatrix
A \B
endbmatrixbiggr) +operatornamerank(C)$$



I have an idea about it:



$$beginbmatrix
A & 0\B & C
endbmatrix=beginbmatrix
A & 0\B & 0
endbmatrix+beginbmatrix
0 & 0\0 & C
endbmatrix$$
.



Now using the inequality, $textrank(A+B)leq textrank(A)+textrank(B)$ results in



$$operatornamerankbiggl(beginbmatrix
A & 0\B & C
endbmatrixbiggr)leq operatornamerankbiggl(beginbmatrix
A \B
endbmatrixbiggr) +operatornamerank(C).$$



The equality holds whenever $Rleft(beginbmatrix
A \B
endbmatrixright) cap R(C)=0$
and $Cleft(beginbmatrix
A \B
endbmatrixright) cap C(C)=0$
.



But how to conclude it in this case?!










share|cite|improve this question











$endgroup$




suppose that $C$ is full column rank matrix,
can we say that the following equality is true:



$$operatornamerankbiggl(beginbmatrix
A & 0\B & C
endbmatrixbiggr)= operatornamerankbiggl(beginbmatrix
A \B
endbmatrixbiggr) +operatornamerank(C)$$



I have an idea about it:



$$beginbmatrix
A & 0\B & C
endbmatrix=beginbmatrix
A & 0\B & 0
endbmatrix+beginbmatrix
0 & 0\0 & C
endbmatrix$$
.



Now using the inequality, $textrank(A+B)leq textrank(A)+textrank(B)$ results in



$$operatornamerankbiggl(beginbmatrix
A & 0\B & C
endbmatrixbiggr)leq operatornamerankbiggl(beginbmatrix
A \B
endbmatrixbiggr) +operatornamerank(C).$$



The equality holds whenever $Rleft(beginbmatrix
A \B
endbmatrixright) cap R(C)=0$
and $Cleft(beginbmatrix
A \B
endbmatrixright) cap C(C)=0$
.



But how to conclude it in this case?!







linear-algebra matrices matrix-rank block-matrices






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited 14 hours ago









Rodrigo de Azevedo

13.1k41960




13.1k41960










asked Sep 17 '18 at 12:43









im hsim hs

345




345











  • $begingroup$
    See this
    $endgroup$
    – user376343
    Sep 17 '18 at 14:55
















  • $begingroup$
    See this
    $endgroup$
    – user376343
    Sep 17 '18 at 14:55















$begingroup$
See this
$endgroup$
– user376343
Sep 17 '18 at 14:55




$begingroup$
See this
$endgroup$
– user376343
Sep 17 '18 at 14:55










1 Answer
1






active

oldest

votes


















2












$begingroup$

You cannot say the equality is true. For example,



$$mathrmrankleft(beginbmatrix0&0\1&1endbmatrixright)neqmathrmrankleft(beginbmatrix0\1endbmatrixright)+mathrmrankleft(beginbmatrix0\1endbmatrixright)$$






share|cite|improve this answer









$endgroup$












  • $begingroup$
    Yes, You are right. But under what conditions we can say that?!
    $endgroup$
    – im hs
    Sep 17 '18 at 12:54










  • $begingroup$
    It should be true since I see this in many papers and books! but without any proof and refer! it seems that it should be trivial!!
    $endgroup$
    – im hs
    Sep 17 '18 at 12:54










  • $begingroup$
    and how about if $A$ is invertible?
    $endgroup$
    – im hs
    Sep 17 '18 at 12:56











  • $begingroup$
    @imhs please refer us to an example of a paper or book saying such a thing. "should be true" says nothing if you are given a counter example.
    $endgroup$
    – GuySa
    Sep 17 '18 at 13:30











  • $begingroup$
    @GuySa please look at this for example: robust model-based fault diagnosis for dynamic systems by Chen and Ron Patton on page 75.
    $endgroup$
    – im hs
    Sep 17 '18 at 16:57











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1 Answer
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oldest

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1 Answer
1






active

oldest

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active

oldest

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active

oldest

votes









2












$begingroup$

You cannot say the equality is true. For example,



$$mathrmrankleft(beginbmatrix0&0\1&1endbmatrixright)neqmathrmrankleft(beginbmatrix0\1endbmatrixright)+mathrmrankleft(beginbmatrix0\1endbmatrixright)$$






share|cite|improve this answer









$endgroup$












  • $begingroup$
    Yes, You are right. But under what conditions we can say that?!
    $endgroup$
    – im hs
    Sep 17 '18 at 12:54










  • $begingroup$
    It should be true since I see this in many papers and books! but without any proof and refer! it seems that it should be trivial!!
    $endgroup$
    – im hs
    Sep 17 '18 at 12:54










  • $begingroup$
    and how about if $A$ is invertible?
    $endgroup$
    – im hs
    Sep 17 '18 at 12:56











  • $begingroup$
    @imhs please refer us to an example of a paper or book saying such a thing. "should be true" says nothing if you are given a counter example.
    $endgroup$
    – GuySa
    Sep 17 '18 at 13:30











  • $begingroup$
    @GuySa please look at this for example: robust model-based fault diagnosis for dynamic systems by Chen and Ron Patton on page 75.
    $endgroup$
    – im hs
    Sep 17 '18 at 16:57
















2












$begingroup$

You cannot say the equality is true. For example,



$$mathrmrankleft(beginbmatrix0&0\1&1endbmatrixright)neqmathrmrankleft(beginbmatrix0\1endbmatrixright)+mathrmrankleft(beginbmatrix0\1endbmatrixright)$$






share|cite|improve this answer









$endgroup$












  • $begingroup$
    Yes, You are right. But under what conditions we can say that?!
    $endgroup$
    – im hs
    Sep 17 '18 at 12:54










  • $begingroup$
    It should be true since I see this in many papers and books! but without any proof and refer! it seems that it should be trivial!!
    $endgroup$
    – im hs
    Sep 17 '18 at 12:54










  • $begingroup$
    and how about if $A$ is invertible?
    $endgroup$
    – im hs
    Sep 17 '18 at 12:56











  • $begingroup$
    @imhs please refer us to an example of a paper or book saying such a thing. "should be true" says nothing if you are given a counter example.
    $endgroup$
    – GuySa
    Sep 17 '18 at 13:30











  • $begingroup$
    @GuySa please look at this for example: robust model-based fault diagnosis for dynamic systems by Chen and Ron Patton on page 75.
    $endgroup$
    – im hs
    Sep 17 '18 at 16:57














2












2








2





$begingroup$

You cannot say the equality is true. For example,



$$mathrmrankleft(beginbmatrix0&0\1&1endbmatrixright)neqmathrmrankleft(beginbmatrix0\1endbmatrixright)+mathrmrankleft(beginbmatrix0\1endbmatrixright)$$






share|cite|improve this answer









$endgroup$



You cannot say the equality is true. For example,



$$mathrmrankleft(beginbmatrix0&0\1&1endbmatrixright)neqmathrmrankleft(beginbmatrix0\1endbmatrixright)+mathrmrankleft(beginbmatrix0\1endbmatrixright)$$







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Sep 17 '18 at 12:45









5xum5xum

91.3k394161




91.3k394161











  • $begingroup$
    Yes, You are right. But under what conditions we can say that?!
    $endgroup$
    – im hs
    Sep 17 '18 at 12:54










  • $begingroup$
    It should be true since I see this in many papers and books! but without any proof and refer! it seems that it should be trivial!!
    $endgroup$
    – im hs
    Sep 17 '18 at 12:54










  • $begingroup$
    and how about if $A$ is invertible?
    $endgroup$
    – im hs
    Sep 17 '18 at 12:56











  • $begingroup$
    @imhs please refer us to an example of a paper or book saying such a thing. "should be true" says nothing if you are given a counter example.
    $endgroup$
    – GuySa
    Sep 17 '18 at 13:30











  • $begingroup$
    @GuySa please look at this for example: robust model-based fault diagnosis for dynamic systems by Chen and Ron Patton on page 75.
    $endgroup$
    – im hs
    Sep 17 '18 at 16:57

















  • $begingroup$
    Yes, You are right. But under what conditions we can say that?!
    $endgroup$
    – im hs
    Sep 17 '18 at 12:54










  • $begingroup$
    It should be true since I see this in many papers and books! but without any proof and refer! it seems that it should be trivial!!
    $endgroup$
    – im hs
    Sep 17 '18 at 12:54










  • $begingroup$
    and how about if $A$ is invertible?
    $endgroup$
    – im hs
    Sep 17 '18 at 12:56











  • $begingroup$
    @imhs please refer us to an example of a paper or book saying such a thing. "should be true" says nothing if you are given a counter example.
    $endgroup$
    – GuySa
    Sep 17 '18 at 13:30











  • $begingroup$
    @GuySa please look at this for example: robust model-based fault diagnosis for dynamic systems by Chen and Ron Patton on page 75.
    $endgroup$
    – im hs
    Sep 17 '18 at 16:57
















$begingroup$
Yes, You are right. But under what conditions we can say that?!
$endgroup$
– im hs
Sep 17 '18 at 12:54




$begingroup$
Yes, You are right. But under what conditions we can say that?!
$endgroup$
– im hs
Sep 17 '18 at 12:54












$begingroup$
It should be true since I see this in many papers and books! but without any proof and refer! it seems that it should be trivial!!
$endgroup$
– im hs
Sep 17 '18 at 12:54




$begingroup$
It should be true since I see this in many papers and books! but without any proof and refer! it seems that it should be trivial!!
$endgroup$
– im hs
Sep 17 '18 at 12:54












$begingroup$
and how about if $A$ is invertible?
$endgroup$
– im hs
Sep 17 '18 at 12:56





$begingroup$
and how about if $A$ is invertible?
$endgroup$
– im hs
Sep 17 '18 at 12:56













$begingroup$
@imhs please refer us to an example of a paper or book saying such a thing. "should be true" says nothing if you are given a counter example.
$endgroup$
– GuySa
Sep 17 '18 at 13:30





$begingroup$
@imhs please refer us to an example of a paper or book saying such a thing. "should be true" says nothing if you are given a counter example.
$endgroup$
– GuySa
Sep 17 '18 at 13:30













$begingroup$
@GuySa please look at this for example: robust model-based fault diagnosis for dynamic systems by Chen and Ron Patton on page 75.
$endgroup$
– im hs
Sep 17 '18 at 16:57





$begingroup$
@GuySa please look at this for example: robust model-based fault diagnosis for dynamic systems by Chen and Ron Patton on page 75.
$endgroup$
– im hs
Sep 17 '18 at 16:57


















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