Thanks a lot!

I didn't thought of doing a list, but ir worked perfectly fine! And it solved both problems at once!

Thanks again

Zguywood

Hi,

When I do exactly this command in maple 9 on a mandriva station, I get

1/6*Heaviside(x+3)-1/6*Heaviside(x-3)+1/6*PIECEWISE([0, x <= -3], [-1, x < 3], [0, 3 <= x])

Here is the file with the example showing differences between defining Delta or not :

View 8506_atmp.mw on MapleNet or Download 8506_atmp.mw
View file details

 Thanks,

Zguywood

Hi,

Actually, I didn't reallised that it worked as long as you don't define Delta. If you specify a value for Delta, either as a local variable, or as a global one, then it doesn't work... and you get for example for Delta:=3;

filtre(Dirac)(x);

 1/6*Heaviside(x+3)-1/6*Heaviside(x-3)+1/6*PIECEWISE([0, x <= -3], [-1, x < 3], [0, 3 <= x]);

The 2 first terms are correct, and the last one is the opposite of the answer... Which leads the sum to 0, I don't know why....

Sorry for my lack of accuracy in the previous description. I hope this time will be clearer.

Zguywood

Hi,

Thanks a lot for this quick and accurate answer! I worked for the 2 examples I showed earlier. I also have another example that I thought somewhat simpler : the top-hat filter now defined as :

filtre:=proc(g) local t;
return x->(1/(2*Delta)*int(g(t),t=(x-Delta)..(x+Delta)));
end;
 

Actually, this one worked even without the "local t" even though I don't get how Maple could evaluate the

int(g(t),t=(t-Delta)..(t+Delta)));

I believed that solving this problem of recursion would solve my other problem but it didn't. I still don't get the expected answer for this particular top-hat filter applied to the dirac function. Maple answers 0 everywhere except in -Delta and +Delta where it is undefined.

The answer I would expect is :

x->PIECEWISE([0, x <= -Delta], [1/(2*Delta), x < Delta], [0, Delta <= x]);

I can input it explicitly for a while, but it's not proper, and I might quickly get lost when I'll use more complex sums of dirac. Do you know where it could come from?

Thanks again!

zguywood