Writing the dirac function as a function handle

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?

Answer 1

[Alan Stevens]

Try

dirac_i = @(x) x==i;   % This assumes i has been fixed before the function is defined 

[Steven Lord]

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