Calculating differences between adjacent elements

[Eilya]

Dear all,
I wonder if there is any easy solution available in Mata for calculating the difference between adjacent elements of a (column) vector? For example, the difference of vector Y should return (Y[2]-Y[1], Y[3]-Y[2], ..., Y[n]-Y[n-1]).
Thank you,
Eilya.

[Niels Henrik Bruun]

Try:

. mata
: y = 1::10
: R = rows(y)
: y[2..R] - y[1..(R-1)]
       1
    +-----+
  1 |  1  |
  2 |  1  |
  3 |  1  |
  4 |  1  |
  5 |  1  |
  6 |  1  |
  7 |  1  |
  8 |  1  |
  9 |  1  |
    +-----+
: end

[Eilya]

Thanks for this, Niels. Works perfectly.

Since I had to calculate the difference many times, I defined a simple function based on what you suggested. While it is simple, it may be worth it to consider including this for the future development of Mata language - for example, Matlab has this built in function.

Best regards,
Eilya.