Question about if command

[Joachim Legh-Smith]

Hello. I have cross-national time-series dataset from 1990 to 2016

I am studying the effect of a decreasing democracy score, and i have a question as i want to create a binary variable that gives a value of 1 if the democracy variable is statistically lower than the year before, and 0 if not, so that i can use an if command to only observe drops in democracy and not increases.

So if for example the variable has a value of 7 in year 1999 and a value of 5 in 2000, the binary variable would then give me a 1.

Furthermore, to check and see how much effect the drop has i have tried to make a variable that is simply the difference of said democracy variable from year to year+1. I tried using a command such as

gen diff = var-(var_n-1]) but that messed it up when it changes countries in the variables

Thank you

[Nick Cox]

Two of various possible ways:

1. works fine without gaps

bysort id (time) : gen diff = var - var[_n-1]

the right-hand side being what I guess you intended to write.

2. works even with gaps

 
tsset id time 
gen diff = D.var

See also

help varlist

Further, watch out: you need the if qualifier, not the if command.

[Joachim Legh-Smith]

Thank you very much that solved it, and i managed to figure the other issue out once that was solved. Thaaank you.