Matlab is not recognizing variables in function handle

Hello all.

I am defining a table of cells that contains function handles.

Why MATLAB cannot recognize them? He cannot access them. I am getting error that MATLAB is not recognizing the variable SS although it is defined. I get error when I type this.

a = P.fw{4}(1:10)

On the other side, when I type this,

a = @(x) 2*SS(4)*x.^0/(BI.L(4))^2

I get answer without error. Any idea why this is happening?

Thanks all.

Answer 1

[Mehmed Saad]

Run following two codes and learn the difference

Code-1 (error will be generated)

clear
fw = {@(x) x+SS;@(x) x+SS+1};
P = table(fw);
%%%%%%%%%%%%%
SS = 1;
%%%%%%%%%%%%%
P.fw{1}(1)

Code-2 (Works fine)

clear
%%%%%%%%%%%%%
SS = 1;
%%%%%%%%%%%%%
fw = {@(x) x+SS;@(x) x+SS+1};
P = table(fw);
P.fw{1}(1)

Also read this comment

[Ahmad Gad]

I understood the trick now. Thanks a lot for the help.

However, I don't need to type the functions in the script file. I need to define them in an input variable P. Can I define them in a variable and call (load) this variable after the SS variable has been assigned a value? MATLAB doesn't accept that idea too.

Any workaounds?

Thanks!

[Steven Lord]

The following will error because varToRemember didn't exist when f was defined and isn't a function that f can call when it is called.

clear varToRemember
f = @(x) x.^varToRemember;
f(3) % will error

Even if we define varToRemember after f was defined, since it didn't exist when f was defined f can't use it.

varToRemember = 2;
f(3)

If the variable exists when the anonymous function is defined, that value will be remembered and used even if the variable changes or is cleared after the anonymous function is defined.

g = @(x) x.^varToRemember;
g(3) % 9, since g "remembers" the value of varToRemember

varToRemember = 3;
g(3) % still 9 not 27

clear varToRemember
g(4) % 16, g remembers

If you want to define an anonymous function that doesn't remember a variable but obtains its value when the anonymous function is evaluated, make that variable an input. Later on you could define a second anonymous function that fixes a value for that input like k fixes varToRemember = 2 when it calls h.

h = @(x, varToRemember) x.^varToRemember;
v = 2;
h(5, v) % 25

k = @(x) h(x, v);
k(6) % 36