CODEWITHSUNDEEP
statadummy-variable
Maesha Armeen
Maesha Armeen

Reputation: 1

Problems in creating dummy variables

The treatment boroughs are five boroughs with ID 1, 2, 3, 6, 14. The “Operation Theseus" policy lasts from week 80 to week 85.

ocu: borough ID

I tried creating dummies of treated and time but they just show as zero for all

gen treated =0 if missing(ocu)==0
replace treated =1 if ocu==1/2/3/6/14
gen time = (week==80-85) & !missing(week)`

Upvotes: 0

Views: 87

Answers (1)

Nick Cox
Nick Cox

Reputation: 37358

ocu == 1/2/3/6/14 is a legal expression, but is likely to be a long way from what you want. 

occ == 1 | occ == 2 | occ == 3 | occ == 6 | occ == 14

is legal and long-winded and 

inlist(occ, 1, 2, 3, 6, 14)

legal and likely to be appealing as an expression for: does occ take on any the values specified?

Although Stata supports | as an "or" operator (and not / for that purpose) note that 

occ == 1 | 2 | 3 | 6 | 14

is legal but almost never what anyone would want, as it is parsed 

(occ == 1) | 2 | 3 | 6 | 14

and will always be evaluated 1 (true), regardless of the value of occ, as just one of the other arguments 2 3 6 14 being non-zero means that the entire expression evaluates to 1 (true).

The expression week==80-85 is also incorrect syntax if you want it to mean week between 80 and 85. Stata will evaluate week == 80-85, applying the subtraction first and so test for equality with -5. See precedence rules as documented in help operators.

The order of evaluation (from first to last) of all operators is ! (or ~), ^, - (negation), /, *, - (subtraction), +, != (or ~=), >, <, <=, >=, ==, &, and |.*

Subtraction comes before testing for equality.

You may want week >= 80 & week <= 85 or inrange(week, 80, 85).

If week is between 80 and 85, then it can't be missing. That test is redundant (but harmless).

Upvotes: 1

Related Questions