problem of function handles, thx

for instance,

parms=ones(2,1);

myfunc = @(parms) X.*parms(1)+Y.*parms(1);

I can directly indicate 'myfunc' in 'fmincon'. [parms,favl]=fmincon(myfunc,parms,....);

However, if I want to separately write 'myfunc' in a function script and then quote it. [parms,favl]=fmincon(myfunc,parms,....); the 'fmincon' will report 'Not enough input in myfunc'.

X and Y are variables stored in workspace, they are not unknown parameters, only parms(1) and parms(2) required estimation.

anyone can tell me how to solve this problem? many thanks!

Answer 1

[Sean de Wolski]

You need an @ before myfunc, otherwise it tries to evaluate it:

@myfunc % reference to function myfunc; do not evaluate
myfunc % when myfunc is its own file tries to run it
myfunc % when myfunc is a function handle (variable), then myfunc is already a reference to whatever

[Zhixiao]

sorry=.= I still do not understand about it, could you please give me some examples? I have read the examples provided by the official website, but I just still do not understand about it... many thanks

[Sean de Wolski]

When you say

myfunc = @(x)x^2

myfunc is now a reference to the function x^2.

if you have a file myfunc2:

function y = myfunc2(x)
y = x^2

And say

myfunc2

It is going to try and call myfunc2. Myfunc2 won't run because it needs x, the error you're getting for not enough inputs.

Since you want to create a reference to myfunc2, you say

myfunc2ref = @myfunc2

Now myfunc2ref is a reference just like myfunc above. You can pass this directly into fminunc.

[Zhixiao]

How can I call function y =myfunc2(x) in fmincon? e.g. 'myfunc2'?

[Sean de Wolski]

fmincon(@myfunc2,etc.)