week8_lec1-2_userdefined_s09

week8_lec1-2_userdefined_s09 - Announcements CANCELLED THIS...

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Announcements CANCELLED THIS WEEK: Prof. Diefes-Dux Office Hours Regularly: Wed 9:30-11 am, ARMS B098 Exam 2 Tuesday March 10, 6:30-7:30 PM ELLT 116 All students with exam conflicts or needing accommodations MUST see Chell Nyquist ( [email protected] ) Upcoming Postings on Blackboard: Learning Objectives Past Exams and Solutions Assigned Seating for the exam
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User-Defined Functions Learning Objectives At the end of this class period, you will begin to be able to: Explain what a user-defined function is in MATLAB Describe at least two reasons why we create user- defined functions in MATLAB Identify at least three essential elements of a user defined function in MATLAB Describe how to pass variables to and from a user- defined function MATLAB Notes pp. 93-95
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Functions Below is a simple view of the overall function of a washing machine The box, representing the function, has inputs, outputs, and “stuff that goes on inside the box” WASH Dirty clothes Clean clothes
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Functions in MATLAB MATLAB functions are similar in that they have: Input Arguments – these are variables (scalars, vectors, matrices, character strings…) Outputs Arguments – these are variables (scalars, vectors, matrices, character strings…) Operations on the Input Arguments Approximate Taylor series Angle Sine of angle Function Operates on Input(s) Input(s) Output(s)
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Functions in MATLAB The format of a function requires that we keep track of input arguments, output arguments, and the function code itself (the stuff in the box) >> x = [3 5 7 9 10] >> y = mean(x) Approximate Taylor series Angle Sine of angle mean function set of data mean value of data input output
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Functions in MATLAB Take a look at a function in MATLAB’s toolbox >> type mean function y = mean(x,dim) %MEAN Average or mean value. % …Help lines… if nargin==1, % Determine which dimension SUM will use dim = min(find(size(x)~=1)); if isempty(dim), dim = 1; end y = sum(x)/size(x,dim); else y = sum(x,dim)/size(x,dim); end Note: You cannot access the code for built-in functions
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Characteristics of MATLAB Functions What happens in a function stays in the function >> x = [5 6; 7 3; -1 10; 1 1] >> mean(x) >> who How a function acts is affected by inputs Example 1: Multiple actions of mean function >> mean(x,1) >> mean(x,2) Example 2: Multiple actions of plot function
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Functions in MATLAB What about when there is no “built-in” function available? Example: Say we want a function that computes the circumference of a circle. …Need user-defined functions ??? radius ??? ???
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Functions in MATLAB Why would I want to create a function in MATLAB? (Team Activity: 1 min) - -
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How does this relate to user-centered design? Everything we just said relates to make MATLAB more
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This note was uploaded on 03/06/2011 for the course ENGR 126 taught by Professor Oakes during the Spring '08 term at Purdue.

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week8_lec1-2_userdefined_s09 - Announcements CANCELLED THIS...

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