Vectors, Part 3

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Previous Lecture

• Questions?
• Arithmetic and Vectors
  • Section 2.3
  • How to multiply vectors
    • Vector times number
    • Vector times vector uses “.*” to avoid matrix multiplication
    • .* does element-by-element multiplication
      • aka “mapping” operation over vector
  • reshape function?
    • Rearranges a vector or matrix into another with the same elements but in a different shape
      

      v = 1:10
      v =
        Columns 1 through 9
           1     2     3     4     5     6     7     8     9
        Column 10
          10
      reshape( v, [2, 5] )
      ans =
           1     3     5     7     9
           2     4     6     8    10
      m = [1 2 3 4; 5 6 7 8; 9 10 11 12]
      m =
      
           1     2     3     4
           5     6     7     8
           9    10    11    12
      reshape( m, [6, 2] )
      ans =
           1     3
           5     7
           9    11
           2     4
           6     8
          10    12

• Lesson 2
  • Manhattan vs Euclidean distance
    
    • mandist function?
    • m-norm of (x₁, x₂, ... , x_n )
    • = ^m√( x₁^m + x₂^m + ... + x_n^m )
    • 1-norm = Manhattan distance
    • 2-norm = Euclidean distance
    • norm function
  • Particularly for large numbers of dimensions, put distances in vector and use operations on whole vector, e.g., sum, etc.
• Next
  • Scripts
  • Section 3.2
  • Optionally Edinburgh video on “Writing a Simple Script” at http://www.see.ed.ac.uk/teaching/courses/matlab/unit03/simple-script.shtml

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