Advanced Functions

Exercise 3
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The sum of geometric series is given by:
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1+r+r2+r3+r4+…+rn
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write a function called “geomser" that will receive a value for r and calculate and return the sum of the geometric series. If a second argument is passed to the function, it is the value of n; otherwise, the function generates a random integer for n ( in the range from 5 to 30). Write you code in the most efficient way.
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Example
function area = areafori(varargin) % areafori returns the area of a circle in feet % a=areafori(radius); calculates the area in foot square % a=areafori(radius,'i'); calculates the area in inch square n=nargin; radius=varargin{1}; if n==2 unit=varargin{2}; if unit == 'i' radius = radius *12; %convert radius from feet to inches else fprintf('input is not identified\n'); end end area = pi*radius.^2;
Anonymous Functions
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Similar to Macros anonymous functions are used to create a quick access to a lengthy statement without having to create a “.m” file for a proper function definition. Syntax:
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Function of Function Using Handlers
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Syntax:
function [outputvars]= function_name(var1,var2,…,funHandler)
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Syntax Example:
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Calling Example:
function sumx= plotfun(x,funh) y=funh(x); plot(x,y); sumx=sum(x(:));
Advanced Functions
Dr. Utayba Mohammad University of Detroit Mercy This Material is adopted from: “Matlab: a practical introduction to programming and problem solving”, Stormy Attaway, 2013
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Variable Output Arguments
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Similar to variable input argument it uses to builtin variables:
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cell array varargout scalar nargout returns the number of variables in the output list at call time.
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load File_name.mat e.g.: >>load ano
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In order to make code more general and adaptable to different inputs “handles” are used by Matlab. Function handles are “function pointers”
function_handler_variable = @ (arguments) function_body;
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function_handler_variable: the name of the function
Anonymous Functions Example
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Create the anonymous function: >> cirarea = @ (radius) pi*radius.^2;
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call the anonymous function: >> area = cirarea(6)
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Get the anonymous function description: >> cirarea
Exercise I
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create anonymous function “cylVol” that calculates the volume of a cylinder.
>>x=0:0.001:2*pi; >>s=plotfun(x,@sin);
Exercise 2
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for the plotting function in the previous example, we’d like to plot the relation between circuit radius and area. use the anonymous function “cirarea” as an input to “plotfun”.
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E.g. given a data set, you want to plot the data and its corresponding fitted model to compare the two. you can pass in the fitting function handler as an input to your plotting function. Syntax: >> handler_var = @function_name; e.g: >> fh = @sin;
Variable Number of Input Arguments
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input variables information can be passed in to a function through
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cell array called varargin (variable argument input) scalar nargin (number of input argument)
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y=calcStat(x); %returns x sorted in ascending order and stores it in y. [y,max]=calcStat(x); [y,max,min]=calcStat(x); [y,max,min,median]=calcStat(x); y=calcStat(x,’descend’);%returns x sorted in descending order and stores it in y. This should work with all output formats as described above y=calcStat(x,’descend’,’First’,k);%returns the first K sorted elements of x in y y=calcStat(x,’First’,k);%returns the first K sorted elements of x in y y=calcStat(x,’descend’,’last’,k);%returns the last K sorted elements of x in y
Saving and importing Anonymous Functions
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you can save anonymous functions in “.mat” file using:
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save File_name.mat anonymous_function_name e.g.: >>save anonfns cirarea
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Variable Input/output Argument Functions
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From Matlab help:
>>help find find Find indices of nonzero elements. I = find(X) returns the linear indices corresponding to the nonzero entries of the array X. X may be a logical expression. Use IND2SUB(SIZE(X),I) to calculate multiple subscripts from the linear indices I. I = find(X,K) returns at most the first K indices corresponding to the nonzero entries of the array X. K must be a positive integer, but can be of any numeric type. I = find(X,K,'first') is the same as I = find(X,K). I = find(X,K,'last') returns at most the last K indices corresponding to the nonzero entries of the array X. [I,J] = find(X,...) returns the row and column indices instead of with sparse matrices. ….