# Writing the dirac function as a function handle

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daniel adams on 30 Sep 2021
Commented: Steven Lord on 30 Sep 2021
Hi I want to write the dirac function at \$i\$ as a function handle, for example the code will look something like this
dirac_i = @(x) 1 if x=i
otherwise 0
end
But I know I cant use if statements in my function handle, so how should I do this?

Alan Stevens on 30 Sep 2021
Try
dirac_i = @(x) x==i; % This assumes i has been fixed before the function is defined
Steven Lord on 30 Sep 2021
If i was not fixed but you want a function handle that makes the appropriate function handle:
diracMaker = @(i) @(x) x == i;
To use call diracMaker to "lock in" the value of i then call the function handle diracMaker returned to evaluate the Dirac "function".
f = diracMaker(2); % f is a function handle that "remembers" its i is equal to 2
x = -5:5;
y = f(-5:5); % Use f
[x; y]
ans = 2×11
-5 -4 -3 -2 -1 0 1 2 3 4 5 0 0 0 0 0 0 0 1 0 0 0
g = diracMaker(1); % g's i is 1, but this doesn't affect f's i
[x; g(x)]
ans = 2×11
-5 -4 -3 -2 -1 0 1 2 3 4 5 0 0 0 0 0 0 1 0 0 0 0
f(1:3) % f still remembers its i is 2
ans = 1×3 logical array
0 1 0