Finding the minimum of a function

2012 10 14
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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

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Star Strider
Star Strider 2012-10-14
I don't see any errors. What were you expecting?
Walter Roberson
Walter Roberson 2012-10-14
The minimum of x^2+1 over 3 to 5 would be 10 not 10.0003

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Walter Roberson
Walter Roberson 2012-10-14

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

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Ping
Ping 2012-10-14
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
Walter Roberson 2012-10-15
[~, fmin] = fmindbnd(funhan,x1,x2);
or
[~, fmin] = fmindbnd(@(x) funhan(x),x1,x2);
Ping
Ping 2012-10-15
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
Walter Roberson 2012-10-15
Which MATLAB version are you using? fminbnd is part of basic MATLAB now. What does
which -all fminbnd
show ?
Ping
Ping 2012-10-15
/Applications/MATLAB_R2012a_Student.app/toolbox/matlab/optimfun/fminbnd.m EDU>>
Walter Roberson
Walter Roberson 2012-10-15
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.

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