Is the row space of a matrix A a subspace A? If so, what are the objects of A?












1












$begingroup$


I have problems with an assertion that I read in a definition of the row space.
I hope somebody can help me :)



This part is clear:
Let A be a mxn-matrix, with rows $ r_{1},...,r_{m} in K^{n} $ The set of all possible linear combinations of $ r_{1},...,r_{m} $ is the row space of A.
Also the row space is a subspace of $K^{n}$.



My Problem:



In one definition that I have read it is stated that the row space of A is also a subspace of A. So the concrete Matrix A has to be a vector space. What are the objects of A?



Can somebody give me an interpretation of what it exactly means that the row space of A is a subspace of A?



PS: I'm not used to write about math in english, please ask if something doesn't makes sense to you.










share|cite|improve this question











$endgroup$












  • $begingroup$
    The phrase "subspace of $A$" is simply nonsense. Does the reference use exactly those words? If not you should tell us exactly what it does say - possibly you're misinterpreting or mistranslating sommething.
    $endgroup$
    – David C. Ullrich
    Jan 9 at 15:24










  • $begingroup$
    sry, I pressed "enter" too soon. The comment I wanted to post: I'm pretty sure that I translated "subspace of A" correctly but it seems like they(my source) made a mistake. I'm already satisfied with the answers (and your comment). Thank you :)
    $endgroup$
    – CherryBlossom1878
    Jan 9 at 19:38


















1












$begingroup$


I have problems with an assertion that I read in a definition of the row space.
I hope somebody can help me :)



This part is clear:
Let A be a mxn-matrix, with rows $ r_{1},...,r_{m} in K^{n} $ The set of all possible linear combinations of $ r_{1},...,r_{m} $ is the row space of A.
Also the row space is a subspace of $K^{n}$.



My Problem:



In one definition that I have read it is stated that the row space of A is also a subspace of A. So the concrete Matrix A has to be a vector space. What are the objects of A?



Can somebody give me an interpretation of what it exactly means that the row space of A is a subspace of A?



PS: I'm not used to write about math in english, please ask if something doesn't makes sense to you.










share|cite|improve this question











$endgroup$












  • $begingroup$
    The phrase "subspace of $A$" is simply nonsense. Does the reference use exactly those words? If not you should tell us exactly what it does say - possibly you're misinterpreting or mistranslating sommething.
    $endgroup$
    – David C. Ullrich
    Jan 9 at 15:24










  • $begingroup$
    sry, I pressed "enter" too soon. The comment I wanted to post: I'm pretty sure that I translated "subspace of A" correctly but it seems like they(my source) made a mistake. I'm already satisfied with the answers (and your comment). Thank you :)
    $endgroup$
    – CherryBlossom1878
    Jan 9 at 19:38
















1












1








1





$begingroup$


I have problems with an assertion that I read in a definition of the row space.
I hope somebody can help me :)



This part is clear:
Let A be a mxn-matrix, with rows $ r_{1},...,r_{m} in K^{n} $ The set of all possible linear combinations of $ r_{1},...,r_{m} $ is the row space of A.
Also the row space is a subspace of $K^{n}$.



My Problem:



In one definition that I have read it is stated that the row space of A is also a subspace of A. So the concrete Matrix A has to be a vector space. What are the objects of A?



Can somebody give me an interpretation of what it exactly means that the row space of A is a subspace of A?



PS: I'm not used to write about math in english, please ask if something doesn't makes sense to you.










share|cite|improve this question











$endgroup$




I have problems with an assertion that I read in a definition of the row space.
I hope somebody can help me :)



This part is clear:
Let A be a mxn-matrix, with rows $ r_{1},...,r_{m} in K^{n} $ The set of all possible linear combinations of $ r_{1},...,r_{m} $ is the row space of A.
Also the row space is a subspace of $K^{n}$.



My Problem:



In one definition that I have read it is stated that the row space of A is also a subspace of A. So the concrete Matrix A has to be a vector space. What are the objects of A?



Can somebody give me an interpretation of what it exactly means that the row space of A is a subspace of A?



PS: I'm not used to write about math in english, please ask if something doesn't makes sense to you.







matrices vector-spaces terminology






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Jan 9 at 14:16









José Carlos Santos

155k22124227




155k22124227










asked Jan 9 at 14:00









CherryBlossom1878CherryBlossom1878

83




83












  • $begingroup$
    The phrase "subspace of $A$" is simply nonsense. Does the reference use exactly those words? If not you should tell us exactly what it does say - possibly you're misinterpreting or mistranslating sommething.
    $endgroup$
    – David C. Ullrich
    Jan 9 at 15:24










  • $begingroup$
    sry, I pressed "enter" too soon. The comment I wanted to post: I'm pretty sure that I translated "subspace of A" correctly but it seems like they(my source) made a mistake. I'm already satisfied with the answers (and your comment). Thank you :)
    $endgroup$
    – CherryBlossom1878
    Jan 9 at 19:38




















  • $begingroup$
    The phrase "subspace of $A$" is simply nonsense. Does the reference use exactly those words? If not you should tell us exactly what it does say - possibly you're misinterpreting or mistranslating sommething.
    $endgroup$
    – David C. Ullrich
    Jan 9 at 15:24










  • $begingroup$
    sry, I pressed "enter" too soon. The comment I wanted to post: I'm pretty sure that I translated "subspace of A" correctly but it seems like they(my source) made a mistake. I'm already satisfied with the answers (and your comment). Thank you :)
    $endgroup$
    – CherryBlossom1878
    Jan 9 at 19:38


















$begingroup$
The phrase "subspace of $A$" is simply nonsense. Does the reference use exactly those words? If not you should tell us exactly what it does say - possibly you're misinterpreting or mistranslating sommething.
$endgroup$
– David C. Ullrich
Jan 9 at 15:24




$begingroup$
The phrase "subspace of $A$" is simply nonsense. Does the reference use exactly those words? If not you should tell us exactly what it does say - possibly you're misinterpreting or mistranslating sommething.
$endgroup$
– David C. Ullrich
Jan 9 at 15:24












$begingroup$
sry, I pressed "enter" too soon. The comment I wanted to post: I'm pretty sure that I translated "subspace of A" correctly but it seems like they(my source) made a mistake. I'm already satisfied with the answers (and your comment). Thank you :)
$endgroup$
– CherryBlossom1878
Jan 9 at 19:38






$begingroup$
sry, I pressed "enter" too soon. The comment I wanted to post: I'm pretty sure that I translated "subspace of A" correctly but it seems like they(my source) made a mistake. I'm already satisfied with the answers (and your comment). Thank you :)
$endgroup$
– CherryBlossom1878
Jan 9 at 19:38












2 Answers
2






active

oldest

votes


















0












$begingroup$

A matrix is not a vector space. Generally, it represents a linear transformation, from one vector space to another.



Now, since the number of columns always equals the dimension of the domain space, we can view the row space as a subspace of $V$ (where $T:Vto W$).






share|cite|improve this answer









$endgroup$













  • $begingroup$
    Thank you for your answer :) If $f:Vrightarrow W $ is a linear transformation and I search for the transformation matrix A of f. Let $ B_{1}={v_{1},...,v_{n}}$ be the basis of V and $ B_{2}={w_{1},...,w_{m}} $ of W, then $f(v_{1})=w=a_{11}w_{1}+...+a_{m1}w_{m}$ with $a_{11},..,a_{m1}$ representing the elements of the first column of A. So if we continue we get n columns which is the dimension of the domain space V, but why should (for example) always $(a_{11},...,a_{1n})^{T}in V$ be true ?
    $endgroup$
    – CherryBlossom1878
    Jan 9 at 20:37












  • $begingroup$
    It's always an $n$-tuple, of elements from the field, so it can be viewed as such.
    $endgroup$
    – Chris Custer
    Jan 9 at 20:41










  • $begingroup$
    Why is it always an n-tuple of elements from the field? If you aren't in the mood to explain it, I would also be happy about a link to a good explanation :)
    $endgroup$
    – CherryBlossom1878
    Jan 9 at 20:54










  • $begingroup$
    I was just thinking I might refer you to Paul Halmos' book Finite Dimensional Vector Spaces. The reason though, that it's an $n$-tuple, where $n=operatorname{dim}V$, is simply that matrix multiplication won't work otherwise. Try a few examples.
    $endgroup$
    – Chris Custer
    Jan 9 at 21:07










  • $begingroup$
    I think that I understand it now, thank you again :) I will check if the book is availible in the library from my university. I think it would be good for my development to also read english literature about math.
    $endgroup$
    – CherryBlossom1878
    Jan 9 at 21:45



















0












$begingroup$

No, a matrix is not a vector space. Asserting that the row space of a matrix is a subspace of that matrix is just an abuse of language.






share|cite|improve this answer









$endgroup$













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    2 Answers
    2






    active

    oldest

    votes








    2 Answers
    2






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    0












    $begingroup$

    A matrix is not a vector space. Generally, it represents a linear transformation, from one vector space to another.



    Now, since the number of columns always equals the dimension of the domain space, we can view the row space as a subspace of $V$ (where $T:Vto W$).






    share|cite|improve this answer









    $endgroup$













    • $begingroup$
      Thank you for your answer :) If $f:Vrightarrow W $ is a linear transformation and I search for the transformation matrix A of f. Let $ B_{1}={v_{1},...,v_{n}}$ be the basis of V and $ B_{2}={w_{1},...,w_{m}} $ of W, then $f(v_{1})=w=a_{11}w_{1}+...+a_{m1}w_{m}$ with $a_{11},..,a_{m1}$ representing the elements of the first column of A. So if we continue we get n columns which is the dimension of the domain space V, but why should (for example) always $(a_{11},...,a_{1n})^{T}in V$ be true ?
      $endgroup$
      – CherryBlossom1878
      Jan 9 at 20:37












    • $begingroup$
      It's always an $n$-tuple, of elements from the field, so it can be viewed as such.
      $endgroup$
      – Chris Custer
      Jan 9 at 20:41










    • $begingroup$
      Why is it always an n-tuple of elements from the field? If you aren't in the mood to explain it, I would also be happy about a link to a good explanation :)
      $endgroup$
      – CherryBlossom1878
      Jan 9 at 20:54










    • $begingroup$
      I was just thinking I might refer you to Paul Halmos' book Finite Dimensional Vector Spaces. The reason though, that it's an $n$-tuple, where $n=operatorname{dim}V$, is simply that matrix multiplication won't work otherwise. Try a few examples.
      $endgroup$
      – Chris Custer
      Jan 9 at 21:07










    • $begingroup$
      I think that I understand it now, thank you again :) I will check if the book is availible in the library from my university. I think it would be good for my development to also read english literature about math.
      $endgroup$
      – CherryBlossom1878
      Jan 9 at 21:45
















    0












    $begingroup$

    A matrix is not a vector space. Generally, it represents a linear transformation, from one vector space to another.



    Now, since the number of columns always equals the dimension of the domain space, we can view the row space as a subspace of $V$ (where $T:Vto W$).






    share|cite|improve this answer









    $endgroup$













    • $begingroup$
      Thank you for your answer :) If $f:Vrightarrow W $ is a linear transformation and I search for the transformation matrix A of f. Let $ B_{1}={v_{1},...,v_{n}}$ be the basis of V and $ B_{2}={w_{1},...,w_{m}} $ of W, then $f(v_{1})=w=a_{11}w_{1}+...+a_{m1}w_{m}$ with $a_{11},..,a_{m1}$ representing the elements of the first column of A. So if we continue we get n columns which is the dimension of the domain space V, but why should (for example) always $(a_{11},...,a_{1n})^{T}in V$ be true ?
      $endgroup$
      – CherryBlossom1878
      Jan 9 at 20:37












    • $begingroup$
      It's always an $n$-tuple, of elements from the field, so it can be viewed as such.
      $endgroup$
      – Chris Custer
      Jan 9 at 20:41










    • $begingroup$
      Why is it always an n-tuple of elements from the field? If you aren't in the mood to explain it, I would also be happy about a link to a good explanation :)
      $endgroup$
      – CherryBlossom1878
      Jan 9 at 20:54










    • $begingroup$
      I was just thinking I might refer you to Paul Halmos' book Finite Dimensional Vector Spaces. The reason though, that it's an $n$-tuple, where $n=operatorname{dim}V$, is simply that matrix multiplication won't work otherwise. Try a few examples.
      $endgroup$
      – Chris Custer
      Jan 9 at 21:07










    • $begingroup$
      I think that I understand it now, thank you again :) I will check if the book is availible in the library from my university. I think it would be good for my development to also read english literature about math.
      $endgroup$
      – CherryBlossom1878
      Jan 9 at 21:45














    0












    0








    0





    $begingroup$

    A matrix is not a vector space. Generally, it represents a linear transformation, from one vector space to another.



    Now, since the number of columns always equals the dimension of the domain space, we can view the row space as a subspace of $V$ (where $T:Vto W$).






    share|cite|improve this answer









    $endgroup$



    A matrix is not a vector space. Generally, it represents a linear transformation, from one vector space to another.



    Now, since the number of columns always equals the dimension of the domain space, we can view the row space as a subspace of $V$ (where $T:Vto W$).







    share|cite|improve this answer












    share|cite|improve this answer



    share|cite|improve this answer










    answered Jan 9 at 14:42









    Chris CusterChris Custer

    11.4k3824




    11.4k3824












    • $begingroup$
      Thank you for your answer :) If $f:Vrightarrow W $ is a linear transformation and I search for the transformation matrix A of f. Let $ B_{1}={v_{1},...,v_{n}}$ be the basis of V and $ B_{2}={w_{1},...,w_{m}} $ of W, then $f(v_{1})=w=a_{11}w_{1}+...+a_{m1}w_{m}$ with $a_{11},..,a_{m1}$ representing the elements of the first column of A. So if we continue we get n columns which is the dimension of the domain space V, but why should (for example) always $(a_{11},...,a_{1n})^{T}in V$ be true ?
      $endgroup$
      – CherryBlossom1878
      Jan 9 at 20:37












    • $begingroup$
      It's always an $n$-tuple, of elements from the field, so it can be viewed as such.
      $endgroup$
      – Chris Custer
      Jan 9 at 20:41










    • $begingroup$
      Why is it always an n-tuple of elements from the field? If you aren't in the mood to explain it, I would also be happy about a link to a good explanation :)
      $endgroup$
      – CherryBlossom1878
      Jan 9 at 20:54










    • $begingroup$
      I was just thinking I might refer you to Paul Halmos' book Finite Dimensional Vector Spaces. The reason though, that it's an $n$-tuple, where $n=operatorname{dim}V$, is simply that matrix multiplication won't work otherwise. Try a few examples.
      $endgroup$
      – Chris Custer
      Jan 9 at 21:07










    • $begingroup$
      I think that I understand it now, thank you again :) I will check if the book is availible in the library from my university. I think it would be good for my development to also read english literature about math.
      $endgroup$
      – CherryBlossom1878
      Jan 9 at 21:45


















    • $begingroup$
      Thank you for your answer :) If $f:Vrightarrow W $ is a linear transformation and I search for the transformation matrix A of f. Let $ B_{1}={v_{1},...,v_{n}}$ be the basis of V and $ B_{2}={w_{1},...,w_{m}} $ of W, then $f(v_{1})=w=a_{11}w_{1}+...+a_{m1}w_{m}$ with $a_{11},..,a_{m1}$ representing the elements of the first column of A. So if we continue we get n columns which is the dimension of the domain space V, but why should (for example) always $(a_{11},...,a_{1n})^{T}in V$ be true ?
      $endgroup$
      – CherryBlossom1878
      Jan 9 at 20:37












    • $begingroup$
      It's always an $n$-tuple, of elements from the field, so it can be viewed as such.
      $endgroup$
      – Chris Custer
      Jan 9 at 20:41










    • $begingroup$
      Why is it always an n-tuple of elements from the field? If you aren't in the mood to explain it, I would also be happy about a link to a good explanation :)
      $endgroup$
      – CherryBlossom1878
      Jan 9 at 20:54










    • $begingroup$
      I was just thinking I might refer you to Paul Halmos' book Finite Dimensional Vector Spaces. The reason though, that it's an $n$-tuple, where $n=operatorname{dim}V$, is simply that matrix multiplication won't work otherwise. Try a few examples.
      $endgroup$
      – Chris Custer
      Jan 9 at 21:07










    • $begingroup$
      I think that I understand it now, thank you again :) I will check if the book is availible in the library from my university. I think it would be good for my development to also read english literature about math.
      $endgroup$
      – CherryBlossom1878
      Jan 9 at 21:45
















    $begingroup$
    Thank you for your answer :) If $f:Vrightarrow W $ is a linear transformation and I search for the transformation matrix A of f. Let $ B_{1}={v_{1},...,v_{n}}$ be the basis of V and $ B_{2}={w_{1},...,w_{m}} $ of W, then $f(v_{1})=w=a_{11}w_{1}+...+a_{m1}w_{m}$ with $a_{11},..,a_{m1}$ representing the elements of the first column of A. So if we continue we get n columns which is the dimension of the domain space V, but why should (for example) always $(a_{11},...,a_{1n})^{T}in V$ be true ?
    $endgroup$
    – CherryBlossom1878
    Jan 9 at 20:37






    $begingroup$
    Thank you for your answer :) If $f:Vrightarrow W $ is a linear transformation and I search for the transformation matrix A of f. Let $ B_{1}={v_{1},...,v_{n}}$ be the basis of V and $ B_{2}={w_{1},...,w_{m}} $ of W, then $f(v_{1})=w=a_{11}w_{1}+...+a_{m1}w_{m}$ with $a_{11},..,a_{m1}$ representing the elements of the first column of A. So if we continue we get n columns which is the dimension of the domain space V, but why should (for example) always $(a_{11},...,a_{1n})^{T}in V$ be true ?
    $endgroup$
    – CherryBlossom1878
    Jan 9 at 20:37














    $begingroup$
    It's always an $n$-tuple, of elements from the field, so it can be viewed as such.
    $endgroup$
    – Chris Custer
    Jan 9 at 20:41




    $begingroup$
    It's always an $n$-tuple, of elements from the field, so it can be viewed as such.
    $endgroup$
    – Chris Custer
    Jan 9 at 20:41












    $begingroup$
    Why is it always an n-tuple of elements from the field? If you aren't in the mood to explain it, I would also be happy about a link to a good explanation :)
    $endgroup$
    – CherryBlossom1878
    Jan 9 at 20:54




    $begingroup$
    Why is it always an n-tuple of elements from the field? If you aren't in the mood to explain it, I would also be happy about a link to a good explanation :)
    $endgroup$
    – CherryBlossom1878
    Jan 9 at 20:54












    $begingroup$
    I was just thinking I might refer you to Paul Halmos' book Finite Dimensional Vector Spaces. The reason though, that it's an $n$-tuple, where $n=operatorname{dim}V$, is simply that matrix multiplication won't work otherwise. Try a few examples.
    $endgroup$
    – Chris Custer
    Jan 9 at 21:07




    $begingroup$
    I was just thinking I might refer you to Paul Halmos' book Finite Dimensional Vector Spaces. The reason though, that it's an $n$-tuple, where $n=operatorname{dim}V$, is simply that matrix multiplication won't work otherwise. Try a few examples.
    $endgroup$
    – Chris Custer
    Jan 9 at 21:07












    $begingroup$
    I think that I understand it now, thank you again :) I will check if the book is availible in the library from my university. I think it would be good for my development to also read english literature about math.
    $endgroup$
    – CherryBlossom1878
    Jan 9 at 21:45




    $begingroup$
    I think that I understand it now, thank you again :) I will check if the book is availible in the library from my university. I think it would be good for my development to also read english literature about math.
    $endgroup$
    – CherryBlossom1878
    Jan 9 at 21:45











    0












    $begingroup$

    No, a matrix is not a vector space. Asserting that the row space of a matrix is a subspace of that matrix is just an abuse of language.






    share|cite|improve this answer









    $endgroup$


















      0












      $begingroup$

      No, a matrix is not a vector space. Asserting that the row space of a matrix is a subspace of that matrix is just an abuse of language.






      share|cite|improve this answer









      $endgroup$
















        0












        0








        0





        $begingroup$

        No, a matrix is not a vector space. Asserting that the row space of a matrix is a subspace of that matrix is just an abuse of language.






        share|cite|improve this answer









        $endgroup$



        No, a matrix is not a vector space. Asserting that the row space of a matrix is a subspace of that matrix is just an abuse of language.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Jan 9 at 14:15









        José Carlos SantosJosé Carlos Santos

        155k22124227




        155k22124227






























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