MATLAB Answers

change parameter values in anonymous function

34 views (last 30 days)
zongxian on 14 Jul 2020
Edited: madhan ravi on 15 Jul 2020
My problem is one function passing to me a Anonymous function handle, for example,
f_handle = function1(a1,a2,....)
% Assuming f_handle = @(x,y) [a*(x+y),b*(x-y)], a and be are unknown parameters
As I only get this handle, (and I know there are two unknown parameters of a and b), now I want to change (set) the parameter values of a and b, I don't know how to do it.
b=1; a=1:10;
x = 1; y =2;
for i=1:10
% how to passing a(i) and b in the anonymouos function
mm{i} = f_handle(x,y);
Should I redefine a anonymous function or by other way?


Sign in to comment.

Accepted Answer

madhan ravi
madhan ravi on 14 Jul 2020
Edited: madhan ravi on 14 Jul 2020
b = 1;
a = 1:10;
x = 1;
y = 2;
mm = cell(1, 10);
f_handle = @(x,y,a,b) [a*(x+y),b*(x-y)];
for ii = 1:10
mm{ii} = f_handle(x,y,a(ii),b);


Show 6 older comments
madhan ravi
madhan ravi on 15 Jul 2020
n = 1; % predefined
f = @(x) x^n
F = func2str(f);
str = regexprep(F,'.*\)','');
SYM = str2sym(str);
"Input in the order of" + char(symvar(SYM))
F_handle = matlabFunction(SYM)
F_handle(2,3) % 2 assigned to n
zongxian on 15 Jul 2020
I also tried to convert it to a string, and then to an anonymous function, but it was not successful. Your way is good, but there is a problem that all variables change to input variables.
for example:
f = @(x) x^n+m ===>
f= @(m,n,x)m+x.^n
If I just want to add a parameter? other parameter sill keep its values
f = @(x) x^n+m ===>
f= @(n,x)m+x.^n
Anyway, I think your method has helped me a lot.
madhan ravi
madhan ravi on 15 Jul 2020
n = 1;
m = 2;
save m
f = @(x) x^n+m
F = func2str(f);
str = regexprep(F,'.*\)','');
SYM = str2sym(str);
clear m
load m
subs(subs(SYM, {x,n},{2,3}))

Sign in to comment.

More Answers (1)

Steven Lord
Steven Lord on 14 Jul 2020
Once you've created an anonymous function handle that "remembers" a particular value, you cannot change that "remembered" value. You would need to recreate the function handle to change it.
n = 2;
f = @(x) x.^n; % n is locked into the value 2 at this point
y1 = f(3) % 9
n = 4;
y2 = f(3) % still 9 not 3^4 = 81
f = @(x) x.^n; % Recreating f "remembers" the new value of n
y3 = f(3) % 81
If you have a value that you want to be able to change, you should probably have the anonymous function accept it. You could, if you need a function with a specific signature, write an adapter. In the example below g accepts both x and n, while f2 and f3 fix specific values for n but make use of g to compute their results.
g = @(x, n) x.^n;
f2 = @(x) g(x, 2);
f3 = @(x) g(x, 3);


Show 1 older comment
Steven Lord
Steven Lord on 15 Jul 2020
In your comment you defined a new function handle F_handle. You didn't modify the existing function handle f.
madhan ravi
madhan ravi on 15 Jul 2020
Right. I misread OPs comment. What I meant by that was there’s an alternative to overcome that problem.

Sign in to comment.

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!