Finding the minimum of a function

My function is supposed to return the minimum y-value, fmin, of the function described in the input function handle, funhan, in the interval, [x1, x2]. What am I doing wrong?

function fmin = findMin(funhan, x1, x2)

[~, fmin] = fmindbnd(@funhan(x),x1,x2);

and I already wrote the pre-exisiting function square_plus_one (which will be called in the test case)

function y = square_plus_one(x)
y= x.^2 + 1

These are what the Test Cases are supposed to run--but i can't run the test cases without an error

>> fh = @square_plus_one;

>> low = 3; hi = 5;

>> findMin(fh,low,hi)

ans = 10.0003

>> fh = @cos;

>> low = 3; hi = 4;

>> findMin(fh,low,hi)

ans = -1.0000

[Star Strider]

I don't see any errors. What were you expecting?

[Walter Roberson]

The minimum of x^2+1 over 3 to 5 would be 10 not 10.0003

Answer 1

[Walter Roberson]

Just pass funhan to fminbnd() instead of passing @funhan(x)

Alternately pass @(x) funhan(x)

[Ping]

walter: when i change my code to

[~, fmin] = @(x) (funhan(x),x1,x2);

I get the error: Expression or statement is incorrect--possibly unbalanced (, {, or [.

and when i change it to

[~, fmin] = @(x) (fminbnd(),x1,x2);

i get the same error! i don't understand the error because all my parenthesis and brackets are in place!

[Walter Roberson]

[~, fmin] = fmindbnd(funhan,x1,x2);

or

[~, fmin] = fmindbnd(@(x) funhan(x),x1,x2);

[Ping]

for the 1st one i get the error: Undefined function 'fmindbnd' for input arguments of type 'function_handle'.

for the 2nd one I get the error: Undefined function 'fmindbnd' for input arguments of type 'function_handle'.

[Walter Roberson]

Which MATLAB version are you using? fminbnd is part of basic MATLAB now. What does

which -all fminbnd

show ?

[Ping]

/Applications/MATLAB_R2012a_Student.app/toolbox/matlab/optimfun/fminbnd.m EDU>>

[Walter Roberson]

fmindbnd() is the same place it was for your original question where you used that function ;-)

Possibly you had a typo in your question and meant to type fminbnd at that point, and that fminbnd is what you want to use here.