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Help with Matric proof!

  1. Feb 14, 2007 #1
    Let A= I - X(X'X)inverseX' to clarify: '=transpose; inverse of quantity (X'X)

    1. Must A be a square matrix?
    2. Must (X'X) be a square matrix?
    3. Must X be a square matrix?
    4. Show whether matrix A is an idempotent matrix (i.e. that AA=A)

    Thanks.
     
  2. jcsd
  3. Feb 14, 2007 #2

    mathwonk

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    im so stupid! i cant follow aNY OF THAT. if i could understand the question i could answer it instantly.
     
  4. Feb 14, 2007 #3
    Sorry. I really would appreciate some help.

    To be more clear: I is an identity matrix

    Questions 1,2,and 3 are essentially Yes/No with a provided proof or explanation.

    Does this help, clarify?

    Thanks.
     
  5. Feb 14, 2007 #4

    mathwonk

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    come on man.
     
  6. Feb 15, 2007 #5
    What do you mean by
    "Let A= I - X(X'X)inverseX' to clarify: '=transpose; inverse of quantity (X'X)"

    Sorry but it's incomprehensible.
     
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