Can I create a vector with a specific pattern in Matlab?

I have this following command:

n=100; ri=1:1:n

I would like to create a new vector according to this pattern: X=[(ri(3)-2*ri(2)+ri(1)),ri(4)-2*ri(3)+ri(2),...,ri(n)-2*ri(n-1)+ri(n-2)].

In words, I would like to create a vector in which its first element is composed by the the third element of ri minus 2*second element of ri plus the first element of ri. The second element would be ri(4)-2*ri(3)+2*ri(2). This pattern would be repeated until ri(n)-2*ri(n-1)+ri(n-2).

Can I create this vector with this specific pattern in Matlab? Sorry If I was not clear in my question.

Thank you very much!

Answer 1

[Azzi Abdelmalek]

n=100;
ri=1:1:n
v=[ ri(3:n)' ri(2:n-1)' ri(1:n-2)' ]
cr=[1 -2 1]
out=sum(bsxfun(@times,v,cr),2)

Or

n=100;
ri=1:1:n
m=3
v=bsxfun(@minus,ri(m:n)',0:m-1)
cr=[1 -2 1]
out=sum(bsxfun(@times,v,cr),2)

[Diego Soares]

Thank you very much!