将Stata循环转换为SPSS循环

Question

Could anyone help with the translation of the following Stata code? I need this code for further analysis in SPSS.

if year<1990 {
    bysort country year ID: egen sum080=sum(PY080g)
    gen hydisp=(HY020+sum080)*HY025
}
else gen hydisp=HY020*HY025

I tried to solve the problem with the following SPSS code:

DO IF year<1990.
   SORT CASES BY country year ID.
   COMPUTE sum080 = SUM(PY080g).
   COMPUTE hydisp=(HY020+sum080)*HY025.
ELSE. 
   COMPUTE hydisp=HY020*HY025.
END IF.
EXECUTE.

But this code appears to be wrong. Do you have any idea how to resolve the problem?

Answer 1

This is in no sense an answer on SPSS code, but it makes a point that would not go well in a comment.

The Stata code

if year < 1990 {
    bysort country year ID: egen sum080=sum(PY080g)
    gen hydisp=(HY020+sum080)*HY025
}
else gen hydisp=HY020*HY025

would get interpreted as

if year[1] < 1990 {
    bysort country year ID: egen sum080=sum(PY080g)
    gen hydisp=(HY020+sum080)*HY025
}
else gen hydisp=HY020*HY025

ie the branching is on the value of year in the first observation (case, record). The if command and the if qualifier are quite different constructs. It seems much more likely that the code desired is something like

bysort country year ID: egen sum080 = sum(PY080g)
gen hydisp = (HY020 + sum080) * HY025 if year < 1990 
replace hydisp = HY020 * HY025 if year >= 1990 

or

bysort country year ID: egen sum080 = sum(PY080g)
gen hydisp = cond(year < 1990, (HY020 + sum080) * HY025, HY020 * HY025) 

The OP's comment that the code appears to be wrong is a poor problem report. What is wrong precisely? It may be nothing more than inability to replicate the results gained in Stata, which would not be surprising as the Stata code is almost certainly not what is intended. It seems unlikely that the first observation is special, but rather that the calculation should be carried out for all observations according to the value of year

Detail: sum() as an egen function is undocumented in favour of total() , but the syntax remains legal.

Detail: The Stata code here would not be considered a loop just because there is a tacit loop over observations.

Answer 2

This particular use of egen in Stata can be replicated in SPSS by using the AGGREGATE command. Using Nick Cox's revised Stata code:

bysort country year ID: egen sum080 = sum(PY080g)
gen hydisp = (HY020 + sum080) * HY025 if year < 1990 
replace hydisp = HY020 * HY025 if year >= 1990 

A synonymous set of code in SPSS would be:

AGGREGATE OUTFILE=* MODE=ADDVARIABLES
  /BREAK = country year ID
  /sum080 = SUM(PY080g).
DO IF Year < 1990.
  COMPUTE hydisp = (HY020+sum080)*HY025.
ELSE.
  COMPUTE hydisp = HY020*HY025.
END IF.