Alternatives to using diff(X,2)

Just a simple question:

We have an alternative for the opreation diff(A,1) given by A(2:end)-A(1:end-1), from an earlier post.

How to generalize it for diff(A,2)? for say A=[1 2 3 4 5 6]? to get [0 0 0 0].

Thanks.

Answer 1

[Bruno Luong]

Just apply the same method twice

D1 = A(2:end)-A(1:end-1);
D2 = D1(2:end)-D1(1:end-1)

or

D2 = conv(A,[1 -2 1],'valid')

[AtoZ]

Perfect, Thanks :)

[AtoZ]

Does it also work for sym type inputs? the conv(..) thing gives error for sym type input while the D2 prescription works.

[Bruno Luong]

No this is numerical difference method