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Atta Oveisi

How to evaluate dirac function in matlab?

Asked by Atta Oveisi
on 23 May 2013

I have this problem in matlab 2011a that I can not evaluate dirac function of higher order. In other words, the symbolic expression works well:

syms x;
diff(dirac(x),x)
ans =
dirac(x, 1)

However, it can not evaluate dirac(x, 1) when x is double:

>> dirac(1, 1)
??? Error using ==> dirac
Too many input arguments.

What should I do? Is there any code available ?

I can evaluate this in Maple but it is hard to believe that matlab doesn't prepared for this simple problem.

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2 Answers

Answer by Iman Ansari
on 23 May 2013
Edited by Iman Ansari
on 23 May 2013
syms x;
y=diff(dirac(x),x)
subs(y,1)

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Answer by Youssef Khmou
on 23 May 2013

hi

The dirac function accepts only one argument (at least for earlier versions than yours) however, if you do not have the symbolic toolbox you can program your own function and put "1" in "0" instead of +infinity .

-First solution :

 t=-10:0.001:10;
 y=dirac(t);
 figure, plot(t,y);
 dy=diff(y)./diff(t);
 figure, plot(t(1:end-1),dy,'r')

-Second solution :

function z=Dirac(t)
N=length(t);
z=zeros(size(t));
for n=1:N
    if t(n)==0
        z(n)=1;
    end
  end

Adjust this function for later use ....

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