Question about keep var[1] ==1 and replace other var ==0

[Liang Wang Jack]

Hi all,

How can I keep var[1] == 1 and other var == 0?

Here is my example:

* Example generated by -dataex-. To install: ssc install dataex
clear
input float(id indi var)
1 3 1
1 3 1
1 3 1
1 3 1
2 5 1
2 5 1
3 4 1
3 4 1
3 4 1
end

data set expect

* Example generated by -dataex-. To install: ssc install dataex
clear
input float(id indi var)
1 3 1
1 3 0
1 3 0
1 3 0
2 5 1
2 5 0
3 4 1
3 4 0
3 4 0
end

Thanks!

[Clyde Schechter]

sort id, stable
by id: replace var = (_n == 1)

[Liang Wang Jack]

sort id, stable
by id: replace var = (_n == 1)

Thank you Clyde. What about the first var is not 1?

For example like this below, the first two value of var are 0, how can I just change the fourth var =0:

* Example generated by -dataex-. To install: ssc install dataex
clear
input float(id indi) str1 tcn float var
1 1 "b" 0
1 1 "a" 0
1 1 "a" 1
1 1 "b" 1
end

data expect

* Example generated by -dataex-. To install: ssc install dataex
clear
input float(id indi) str1 tcn float var
1 1 "b" 0
1 1 "a" 0
1 1 "a" 1
1 1 "b" 0
end

Thank you again!

[Clyde Schechter]

The following code assumes that var takes on only 0 and 1 values, and begins by verifying the assumption.

assert inlist(var, 0, 1)
sort id, stable
by id: replace var = sum(var)
replace var = 0 if var != 1