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MATLAB Functions, feval, inline functions, by vts15196


									                                     K. Alavi:

     MATLAB Functions, feval, inline functions
1.    Function Definition Line

      a. For 3 outputs u, v, w and 2 inputs x, y

       function[u,v,w] = yourfun (x,y)

      b.   For 1 output W and three inputs x, y, z

            function[W]= myfun(x,y,z])
            OR equivalently
            function W = myfun (x,y,z])

      c.   For function with no output and 3 inputs

            function[ ]= ellipse(L,S,theta)
           OR equivalently
            Function = ellipse(L,S,theta)

           This could be for a function that draws an ellipse
           with major & minor axes L and S and rotation theta

2.    Function Call

       General: we have to give values for the inputs and
       use variable name that store the values of the
       outputs. Below are examples of how the above
       functions are called

       a. [A,B,C] = yourfun(-5,4)
           This means that input values are x=-5, y=4, and
           output values for A, B, and C, are calculated
           according to the function prescription

       b. [M] = myfun(2,4,-3)
             OR equivalently
             M = myfun(2,4,-3)

       c. ellipse(10,5,pi/6)
3.    The feval Command

This command evaluates the values of the output variables
for a function for given values of the inputs. For example
we can find values for the outputs of yourfun for input
values of x=-5 and y=4 using feval in the following manner:

     [a,b,c] = feval(‘yourfun’,-4,5)

      or alternatively we can define a function handle for
      yourfun, call it func1 and use it with feval:

     func1 =@yourfun
     [a,b,c] = feval(func1,-4,5)

4.    The inline Command

This command is used to generate a function in the command
window or within a script file or a function file. For
example for a function of 3 variables x, y, z we have

Function-name =inline(“math formula’,’x’,’y’,’z’)
Here the formula and the input variable names are in single
quotes. For example the following inline function to
evaluate distance between two vectors Ra and Rb with angle
ab between them:


Note that because the statement was too long we used ... for
continuation. In the command file the following will appear:

      Inline function:

      Distance(Ra,Rb,ab)= sqrt(Ra.^2+Rb.^2...
To use this, we give values for Ra, Rb, and ab, say, Ra=3,
Rb=4, and ab=pi/4 type Distance(3,4,pi/4). The value for
Distance will be then evaluated for the given input values.
Note if you use arrays for Ra, Rb, and ab, you can get
distance for as many vector pairs as you want.

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