Product of matrices multiplying each row by corresponding column

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I was wondering if there exists a certain type of matrix multiplication that just multiplies row $i$ by column $i$. For example let be



$$
A=beginbmatrix
a_11 & a_12 & a_13 \
a_21 & a_22 & a_23 \
a_31 & a_32 & a_33 \
endbmatrix
$$



I want to represent the following matrix:



$$
B=beginbmatrix
sum_i=1^3 a_i1^2 & sum_i=1^3 a_i2^2 & sum_i=1^3 a_i3^2 \
endbmatrix
$$



I can define $B=operatornamediag(A^TA)$, but I was wondering if there exists a type of product for representing $B$.







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    up vote
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    down vote

    favorite












    I was wondering if there exists a certain type of matrix multiplication that just multiplies row $i$ by column $i$. For example let be



    $$
    A=beginbmatrix
    a_11 & a_12 & a_13 \
    a_21 & a_22 & a_23 \
    a_31 & a_32 & a_33 \
    endbmatrix
    $$



    I want to represent the following matrix:



    $$
    B=beginbmatrix
    sum_i=1^3 a_i1^2 & sum_i=1^3 a_i2^2 & sum_i=1^3 a_i3^2 \
    endbmatrix
    $$



    I can define $B=operatornamediag(A^TA)$, but I was wondering if there exists a type of product for representing $B$.







    share|cite|improve this question























      up vote
      0
      down vote

      favorite









      up vote
      0
      down vote

      favorite











      I was wondering if there exists a certain type of matrix multiplication that just multiplies row $i$ by column $i$. For example let be



      $$
      A=beginbmatrix
      a_11 & a_12 & a_13 \
      a_21 & a_22 & a_23 \
      a_31 & a_32 & a_33 \
      endbmatrix
      $$



      I want to represent the following matrix:



      $$
      B=beginbmatrix
      sum_i=1^3 a_i1^2 & sum_i=1^3 a_i2^2 & sum_i=1^3 a_i3^2 \
      endbmatrix
      $$



      I can define $B=operatornamediag(A^TA)$, but I was wondering if there exists a type of product for representing $B$.







      share|cite|improve this question













      I was wondering if there exists a certain type of matrix multiplication that just multiplies row $i$ by column $i$. For example let be



      $$
      A=beginbmatrix
      a_11 & a_12 & a_13 \
      a_21 & a_22 & a_23 \
      a_31 & a_32 & a_33 \
      endbmatrix
      $$



      I want to represent the following matrix:



      $$
      B=beginbmatrix
      sum_i=1^3 a_i1^2 & sum_i=1^3 a_i2^2 & sum_i=1^3 a_i3^2 \
      endbmatrix
      $$



      I can define $B=operatornamediag(A^TA)$, but I was wondering if there exists a type of product for representing $B$.









      share|cite|improve this question












      share|cite|improve this question




      share|cite|improve this question








      edited Jul 28 at 18:04









      Daniel Buck

      2,2841623




      2,2841623









      asked Jul 28 at 17:29









      coolsv

      687




      687




















          1 Answer
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          At the top of my head it doesn't seem like such operation would exist! By just for fun you could try to see the properties that such operation should have, maybe you get something interesting out of it!



          The only "less known", I put it in quotation marks just because it's not totally true that isn't known but respect to classic matrix multiplication it is, is the Kroneker product defined as: given two matrices $A$ and $B$, their Kronecker product is as follows $$Aotimes B=left(beginmatrixa_11B&a_12B&cdots&a_1nB\a_21B&a_22B&cdots&a_2nB\vdots&vdots&ddots&vdots\a_n1B&a_n2B&cdots&a_nnBendmatrixright)$$






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          • Yeah Davide. I only know the Kronecker product and the Hadamard product! So perhaps there's no such product as you mentioned! Thanks
            – coolsv
            Jul 29 at 4:44










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          1 Answer
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          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes








          up vote
          1
          down vote



          accepted










          At the top of my head it doesn't seem like such operation would exist! By just for fun you could try to see the properties that such operation should have, maybe you get something interesting out of it!



          The only "less known", I put it in quotation marks just because it's not totally true that isn't known but respect to classic matrix multiplication it is, is the Kroneker product defined as: given two matrices $A$ and $B$, their Kronecker product is as follows $$Aotimes B=left(beginmatrixa_11B&a_12B&cdots&a_1nB\a_21B&a_22B&cdots&a_2nB\vdots&vdots&ddots&vdots\a_n1B&a_n2B&cdots&a_nnBendmatrixright)$$






          share|cite|improve this answer





















          • Yeah Davide. I only know the Kronecker product and the Hadamard product! So perhaps there's no such product as you mentioned! Thanks
            – coolsv
            Jul 29 at 4:44














          up vote
          1
          down vote



          accepted










          At the top of my head it doesn't seem like such operation would exist! By just for fun you could try to see the properties that such operation should have, maybe you get something interesting out of it!



          The only "less known", I put it in quotation marks just because it's not totally true that isn't known but respect to classic matrix multiplication it is, is the Kroneker product defined as: given two matrices $A$ and $B$, their Kronecker product is as follows $$Aotimes B=left(beginmatrixa_11B&a_12B&cdots&a_1nB\a_21B&a_22B&cdots&a_2nB\vdots&vdots&ddots&vdots\a_n1B&a_n2B&cdots&a_nnBendmatrixright)$$






          share|cite|improve this answer





















          • Yeah Davide. I only know the Kronecker product and the Hadamard product! So perhaps there's no such product as you mentioned! Thanks
            – coolsv
            Jul 29 at 4:44












          up vote
          1
          down vote



          accepted







          up vote
          1
          down vote



          accepted






          At the top of my head it doesn't seem like such operation would exist! By just for fun you could try to see the properties that such operation should have, maybe you get something interesting out of it!



          The only "less known", I put it in quotation marks just because it's not totally true that isn't known but respect to classic matrix multiplication it is, is the Kroneker product defined as: given two matrices $A$ and $B$, their Kronecker product is as follows $$Aotimes B=left(beginmatrixa_11B&a_12B&cdots&a_1nB\a_21B&a_22B&cdots&a_2nB\vdots&vdots&ddots&vdots\a_n1B&a_n2B&cdots&a_nnBendmatrixright)$$






          share|cite|improve this answer













          At the top of my head it doesn't seem like such operation would exist! By just for fun you could try to see the properties that such operation should have, maybe you get something interesting out of it!



          The only "less known", I put it in quotation marks just because it's not totally true that isn't known but respect to classic matrix multiplication it is, is the Kroneker product defined as: given two matrices $A$ and $B$, their Kronecker product is as follows $$Aotimes B=left(beginmatrixa_11B&a_12B&cdots&a_1nB\a_21B&a_22B&cdots&a_2nB\vdots&vdots&ddots&vdots\a_n1B&a_n2B&cdots&a_nnBendmatrixright)$$







          share|cite|improve this answer













          share|cite|improve this answer



          share|cite|improve this answer











          answered Jul 28 at 19:26









          Davide Morgante

          1,728220




          1,728220











          • Yeah Davide. I only know the Kronecker product and the Hadamard product! So perhaps there's no such product as you mentioned! Thanks
            – coolsv
            Jul 29 at 4:44
















          • Yeah Davide. I only know the Kronecker product and the Hadamard product! So perhaps there's no such product as you mentioned! Thanks
            – coolsv
            Jul 29 at 4:44















          Yeah Davide. I only know the Kronecker product and the Hadamard product! So perhaps there's no such product as you mentioned! Thanks
          – coolsv
          Jul 29 at 4:44




          Yeah Davide. I only know the Kronecker product and the Hadamard product! So perhaps there's no such product as you mentioned! Thanks
          – coolsv
          Jul 29 at 4:44












           

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