Question on Order of Operations

[Roy Wang]

Hello I am new to STATA and noticed a difference in the following lines of code:

replace var = 1 if dup_counter[_n] != 0 & dup_counter[_n+1] != 0 & (var[_n+1]>var[_n] | var[_n]>var[_n+1])

replace var = 1 if dup_counter[_n] != 0 & dup_counter[_n+1] != 0 & var[_n+1]>var[_n] | var[_n]>var[_n+1]

Why do the parentheses matter? The 1st line of code only modified 40 results while the 2nd modified several hundred.

Some duplicates had missing value (.) and other had values of 1 within a group of duplicates. The goal was to change all the missing within a duplicate group to 1.

[Clyde Schechter]

The parentheses matter for the same reason that they matter in 2*(3+4) vs 2*3+4. Just as multiplication takes precedence over addition, & takes precedence over |.

[daniel klein]

From

help operator

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

As for the problem, Roy probably wants to sort before the replace commands; details of code depend on the details of the problem, of which we only see a presumably last step.

Best
Daniel