Branch Statements

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• Misc
  • Math department scholarships
    • Open to sophomores and juniors
    • Apply by March 23
    • See email invitation and/or dept. scholarships web page (https://www.geneseo.edu/math/scholarships)
  • PRISM Mentoring
    • Wednesday, March 9, 3:30
    • South 328
    • Advice from math majors re course selection, summer experiences, etc.
• Friday’s Online Class
  • Result is at https://docs.google.com/document/d/1_k8kZC1DuwyIYmFGOi5Q9FU6GgD7-YO4-rpXdtZQ5e8/edit
  • I’d be happy to hear any comments, feedback, etc. you have
• Questions?
  • Incorporating transformation into stickPerson function?
    • Key idea is to multiply transformation as a matrix and points defining the stick person together and then draw the resulting points
• If Statements
  • Sections 12.1 and 12.2
    • Branching = splitting program according to logical expression
    • Syntax
      

      if ( logical_expression )
      	statements1  % done if expression is true
      else
      	statements2  % done if expression is false
      end

    • elseif for nesting inside if
  • Examples
    • Text’s animations
      • To use these examples in the command window you need to define age first:
        

        >> if ( age < 25 )
        price = 4800;
        else
        price = 2200;
        end
        Undefined function or variable 'age'. 

      • If age is defined, you can type branches into the command window, Matlab will wait until the whole thing is entered and then execute it
        

        >> age = 30;
        >> if ( age < 25 )
        price = 4800;
        else
        price = 2200;
        end
        >> price
        price =
                2200

      • But it would be more common to put such code into a function (or script)
        

        function [price] = insure( age )
        if ( age < 25 )
            price = 4800;
        else
            price = 2200;
        end
        end

      • That function could then be called with appropriate values
        

        >> insure( 17 )
        ans =
                4800
        >> insure( 30 )
        ans =
                2200

    • Absolute value as a function defined piecewise
      • Mathematically, abs(x) =…
        • -x if x < 0
        • x if x ≥ 0
      • in Matlab…
        

        function [y] = absvalue( x )
        if ( x < 0 ) 
            y = -x;
        else
            y = x;
        end
        end

      • Some example calls:
        

        >> absvalue( -7 )
        ans =
             7
        >> absvalue( 3.7 )
        ans =
            3.7000

  • Lab re “if” and piecewise function definitions
    • Handout
• Next
  • Recursive function definitions
  • No reading

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