Column Vectors and “Reduce” Operations

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• Questions?
• Column Vectors & Reduce Operations
  • Section 5.14
    • Column array
      • Semicolon instead of comma
    • Transpose?
      • Via single quote operator or transpose function
        

        >> v = 1 : 5
        v =
            1     2     3     4     5
        >> v'
        ans =
            1
            2
            3
            4
            5
        >> transpose( v )
        ans =
            1
            2
            3
            4
            5

    • Operations on row vectors generally work on columns too
  • Section 7.9
    • Functions for mean, standard deviation, median, mode other statistical analyses
    • max has 2 results, value and position
  • Two other reduce operations
    • sum: compute the sum of all elements in a vector
    • prod: compute product of all elements in a vector
      

      >> sum( v )
      ans =
          15
      >> prod( v )
      ans =
          120

  • Examples
    • Statistics on heights of people from class
      

      >> heights = [ 5*12+10, 5*12+7, 5*12+2, 5*12+10, 5*12+4, 5*12+11, 5*12+4, 6*12+1, 5*12+11 ]
      heights =
          70    67    62    70    64    71    64    73    71
      >> mean( heights )
      ans =
          68
      >> mode( heights )
      ans =
          64
      >> mode( heights(end:-1:1) )
      ans =
          64
      >> std( heights' )
      ans =
          3.8730

• Vector Lab
• Next
  • Nyquist’s Theorem; finish vector lab
  • No required reading, but…
    • If you finish the lab, experimenting with Nyquist’s Theorem in real sounds is fun — optionally read section 7.2 for some Matlab functions that let you do it
    • Bring headphones to class if you want to try out Matlab sound

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