st: How to identify two consequtives values of a variable

["Pablo.CARVALLO" <pablocepal@gmail.com>]

Hi Statalist,

I create a variable x which states a local max (1), a local min(-1),
and 0 in other case. If x==1, the following value may be 0 or -1, but
it cannot be 1 again. For example, an 'ideal' x may be:

x
--
0
0
1
0
0
0
0
-1
0
0
1
-1
0
0
0
1

But I have something like this:

x
--
0
0
1
0
0
0
0
1 ----> this value is wrong, because previous x different from 0 was 1.
0
0
-1
1
0
0
0
-1

I need a variable 'y' which tells me when x takes this wrong values:

x     y
---------
0     0
0     0
1     0
0     0
0     0
0     0
0     0
1     1 ---> y==1
0     0
0     0
-1    0
1     0
0     0
0     0
0     0
-1    0

Thanks a lot!

Pablo Carvallo
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