Implement sliding window for vector

I have an ecg data vector X(n), with size 3,000 for which I want to get the Gradient G using the following formula:

G(n)=Xmax(w)-Xmin(w),

where: w is is a rectangular sliding window of size 11, centered at nth element, Xmax is the maximum value of X(n) within the window and Xmin is the minimum value of X(n) within the window.

How can I do that?

I know I can use a loop, but how to get window of 11 elements for the first and last 5 elements in the vector X(n)? for example: for X(6), I use X(1:5) as half of the window and the other half zeros? Help please.