Matlab’s Built-In Functions

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• Misc
  • Math Learning Center is now open
    • Short version: M-F midday, M-R evenings
    • South 332
    • Details at http://www.geneseo.edu/math/mlc
  • Google group (i.e., mailing list) for this class
    • math230-02-spr16-googlegroup@geneseo.edu
    • Also shares this document
• Questions?
• Built-In Functions
  • Section 2.2
    • Built-in functions: trig, inverse trig, exponential, logs to different bases
    • Syntax
      • name( argument )
    • Tab completion to find names
    • Help with function meaning
    • Function names are variable names and can be changed
  • Examples
    • Managing Matlab session; how I set mine up
      

      >> format compact
      >> diary jan27
      >> clc
      >> x = 1
      x =
           1
      >> y = 17
      y =
          17
      >> clear
      >> x = 1
      x =
           1
      >> y = 17
      y =
          17
      >> clear x

    • Check that for your favorite angle, sin²x + cos²x = 1
      

      >> angle = pi/6
      angle =
          0.5236
      >> sin(angle)^2 + cos(angle)^2
      ans =
           1

    • How about sec²x - tan²x?
      

      >> sec(angle)^2 - tan(angle)^2
      ans =
           1

    • Find out what the abs function does and how to call it
      

      >> help abs
       abs    Absolute value.
          abs(X) is the absolute value of the elements of X. When
          X is complex, abs(X) is the complex modulus (magnitude) of
          the elements of X.
       
          See also sign, angle, unwrap, hypot.
      
          Other functions named abs
      
          Reference page in Help browser
             doc abs

    • Rounding functions: round, floor, ceil
      

      >> round( 3.2 )
      ans =
           3
      >> floor( 3.9 )
      ans =
           3
      >> ceil( 3.1 )
      ans =
           4

    • Why atan vs atan2?
      • Has to do with inverse tangent often being used to find angle between the line to a point and the X axis
        
        

        >> atan( 1 )
        ans =
            0.7854
        >> atan2( 1, 1 )
        ans =
            0.7854
        >> atan2( -1, -1 )
        ans =
           -2.3562

  • A model for what happens when you call a function
    
• Lab 1
  • Handout
  • Quick intro to scripts
    • Matlab code saved in a text file to be executed without having to retype it
    • File names must end with “.m”
    • Use “New Script” button in Matlab toolbar to open an editor for writing a script
    • “Save” and “Run” buttons in editor toolbar save the file and run the code in it, respectively
• Next
  • Variables
  • Read sections 3.1 through 3.7

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