MATLAB课程：代码示例之Programming（四）

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收藏 2016-03-09

MATLAB课程：代码示例之Programming（四）

Anonymous Functions

This example shows how to define functions at the command line with anonymous functions.

Integrating a Function

Consider the function 10*x.

If we want to allow any multiplier of x, not just 10, we might create a variable g (where g is initially set to 10), and create a new function

Let's do this in MATLAB® by creating a function handle h.

g = 10;h = @(x) g*x;

You can integrate the function by passing its handle to the INTEGRAL function.

integral(h,1,10)

ans = 495.0000

Consider another function:

Create a function handle to this function where alpha = 0.9.

alpha = 0.9;f = @(x) sin(alpha*x);

Plot the function and shade the area under it.

x = 0:pi/100:pi;area(x,f(x)); % You can evaluate f without fevaltitle('f(x) = sin(\alpha x), \alpha =.9');

We can use the INTEGRAL function to calculate the area under the function between a range of values.

integral(f,0,pi)

ans = 2.1678

Minimizing a Function

Consider the function:

where a = 1, b = -2, and c = 1

Create a function handle for it.

a = 1;b = -2;c = 1;f = @(x)(a*x.^2+b*x+c);

ezplot(f); % Plot the functiontitle('f(x)=ax^2+bx+c, a=1,b=-2,c=1');hold on;% Find and plot the minimumminimum = fminbnd(f,-2,2); % We can pass the function handle directly % to the minimization routineplot(minimum,f(minimum),'d'); % We can evaluate the function without % using fevalgrid;hold off;