I need help using the feval command

Write a function to define fx=@(x) 1/((x-.3)^2+.01)+1/((x-.9)^2+.04)-6 a) Plot this function using fplot command between 0 and 2. b) Determine zero of this function in the above interval. c) Determine for which x the function will be maximum in the above interval. d) What is the maximum value of the function f(x). (hint: look for feval command) I got most of it but I am lost on using the feval command.

Answer 1

[Youssef Khmou]

hi, To analyze your function, you must add the element wise operator to avoid the error of ' Matrix must be square', here is a version :

fx=@(x) 1./((x-.3).^2+.01)+1./((x-.9).^2+.04)-6
fplot(fx,[0 2])
grid on
z=fzero(fx,[0 2]);

In the next, i propose to use a predefined linear vector x, then apply the feval command on it :

 N=1000;        % Resolution
 x=linspace(0,2,N);
 [a,b]=max(feval(fx,x));

a represents the maximum value which is : 96.5014, to get the value of x, which is related to a sample rate of the vector x, proceed as the following :

 Ts=2/N; %  Inverse of the sample rate .
 b=b*Ts;

Summary :

The function passes through the x axis at x=1.2995, has maximum value of M=96.5041 that corresponds to x=0.3020 .

[Chris]

Thank you so much. Matlab is so confusing.