Writing the dirac function as a function handle

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daniel adams 2021-9-30

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https://ww2.mathworks.cn/matlabcentral/answers/1464049-writing-the-dirac-function-as-a-function-handle

评论： Steven Lord 2021-9-30

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?

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Answer 1

Alan Stevens 2021-9-30

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https://ww2.mathworks.cn/matlabcentral/answers/1464049-writing-the-dirac-function-as-a-function-handle#answer_798699

在 MATLAB Online 中打开

Try

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

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Steven Lord 2021-9-30

在 MATLAB Online 中打开

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