Local Minimum in MATLAB? -

i'm trying find exact minimum of simple function in matlab. i've been experimenting use of built-in functions such "fminbnd" , inline function definition, don't think quite know i'm doing.

my code below. want find x , y of error's minimum.

clear  = 5; tau = linspace(1,4,500); %array of many tau values between 1 , 4 e1 = qfunc(((-tau) + 5) /(sqrt(2.5))); e0 = qfunc((tau)/(sqrt(2.5)));  error = 0.5*e0 + 0.5*e1;  figure subplot (311), plot(tau, e0); xlabel('threshold (tau)'), ylabel('e0') title('error vs. threshold (e0, 1 <= t <= 4)') subplot (312), plot(tau, e1); xlabel('threshold (tau)'), ylabel('e1') title('error vs. threshold (e1, 1 <= t <= 4)') subplot (313), plot(tau, error); xlabel('threshold (tau)'), ylabel('pr[error]'); title('error vs. threshold (pr[error], 1 <= t <= 4)') 

i mean, can use cursor when function graphed close (though not right @ point occurs (threshold = 2.5), there must method print number window. far have tried:

fminbnd('error', 'e0', 'e1') 

and many other variants. tried using anonymous , inline function definitions no luck.

can point me in right direction? feel foolish being stuck simple problem... appreciated!

see fminbnd

you should try this:

error =@(tau) 0.5*qfunc(((-tau) + 5) /(sqrt(2.5))) + 0.5*qfunc((tau)/(sqrt(2.5))); x = fminbnd(error,0,10) 

the first argument of fminbnd(f,x1,x2) function , other arguments bounds. did f=error, x1=0 , x2=10.

output:

x=2.5000

another way save error function in .m file. see webpage above.