I want to make pre/post column using id and standard column.

pre column is the result of raising the standard by one cell.
post column is the result of lowering the standard by one cell.

Data is weekly, so there are time variables, but it is difficult to use them.
( ex. 01dec2015 = First week of december 2015 )

I need your help.
What should I do?


Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input str6 id float(pre standard post)
"A00011" 1 0 0
"A00011" 1 1 0
"A00011" 2 1 1
"A00011" 2 2 1
"A00011" 3 2 2
"A00011" 3 3 2
"A00011" 2 3 3
"A00011" 2 2 3
"A00011" 3 2 2
"A00011" 0 3 2
"A00560" 1 1 0
"A00560" 2 1 1
"A00560" 2 2 1
"A00560" 3 2 2
"A00560" 2 3 2
"A00560" 1 2 3
"A00560" 3 1 2
"A00560" 4 3 1
"A00560" 0 4 3
end