Summary and Statistical Operations on Arrays

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• Misc
  • Friday (Mar. 4) class
    • I’ll be out of town
    • Class will be online review of exam solutions during normal class time
    • Open this Google doc to participate
  • Exam 1
    • Wednesday (Mar. 2)
    • Material since beginning of semester (e.g., expressions, variables, vectors, plotting, matrices, functions, scripts, etc.)
    • 3 - 5 short-answer questions, may include writing short pieces of Matlab
    • Practice exam at http://www.geneseo.edu/~baldwin/math230/spring2016/exam1sample.pdf
    • Whole class period (50 minutes)
    • Open references (book, notes, computer); closed person
• Questions?
  • One appointment for lab 4 and project is fine (half hour)
• Summarizing Vector/Matrix Contents
  • Sometimes called “reduce” operations in contrast to “map”
  • Sections 7.9 and 9.5
    • 7.9: statistics
      • Set of numbers in vector or matrix
      • Such operations as mean, std, median, mode, max, min, range
    • 9.5: expands to matrices
      • Difference from vectors?
        • Mainly that statistics are collected down each column rather than for matrix as a whole
  • Examples
    

    >> % Vector of peoples heights
    >> heights = [ 5*12+10, 5*12+7, 5*12+4, 5*12+6, 5*12+7 ]
    heights =
        70    67    64    66    67
    >> mean( heights )
    ans =
       66.8000
    >> sum( heights )
    ans =
       334
    % Statistics on a matrix
    >> m = [ 1, 2, 3; 4, 5, 6]
    m =
         1     2     3
         4     5     6
    >> mean(m)
    ans =
        2.5000    3.5000    4.5000
    >> heightsAndAges = [ 60 18; 66 20; 70 69]
    heightsAndAges =
        60    18
        66    20
        70    69
    >> mean(heightsAndAges)
    ans =
       65.3333   35.6667
    % Find maximum of all heights and ages
    >> max( heightsAndAges )
    ans =
        70    69
    >> max( max( heightsAndAges) )
    ans =
        70
    >> sum( sum( heightsAndAges ) )
    ans =
       303

• Matrix Lab
• Next
  • (Monday - After exam and review)
  • “If” statements
  • Read sections 12.1 and 12.2
  • Optionally sections 12.3 and 12.4 to review relational and logical operations

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