This synthetic example shows that the command will list precisely those
observations that differ from the previous observation. But this
includes the first, as city[0] evaluates to string missing, i.e. "".
More generally, varname[0] is regarded as missing in the sense of the
variable's data type, i.e. numeric missing . or string missing "". So
the first in each group will always be listed (unless its value is
missing).
. l
+------------+
| city |
|------------|
1. | Durham, UK |
2. | Durham, UK |
3. | Durham, UK |
4. | Durham, NC |
5. | Durham, NC |
|------------|
6. | Durham, NH |
7. | Durham, NH |
8. | Durham, NH |
9. | Durham, NH |
10. | Durham, NH |
+------------+
. list if city != city[_n-1]
+------------+
| city |
|------------|
1. | Durham, UK |
4. | Durham, NC |
6. | Durham, NH |
+------------+
You probably want
by id : gen prev = city[1]
by id : list prev city if prev != city & _n == 2
There is no royal road to cleaning up string variables. The matter was
discussed on the list earlier this year and written up as a Tip:
SJ-8-3 dm0039 . . . Stata tip 64: Cleaning up user-entered string
variables
. . . . . . . . . . . . . . . . . . . . . . . . J. Herrin and
E. Poen
Q3/08 SJ 8(3):444--445 (no
commands)
tip on how to clean up user-entered string variables
Nick
[email protected]
Rijo John
I have a data set as follows
ID City Year
1 City name 1
1 City name 2
The data is suppose to have same city names for each ids for year 1
and two. but there are many occasions where city for the year 1 is
spelt differently thanthat for year 2. I just want to list out or edit
those cities where city names are different for year 1 and 2 for the
same ID. When I issue the following command
bysort ID : list if City!=City[_n-1]
it lists all observations in the data whether or not the city is spelt
differently in years one and two. Thats strange to me? Can someone
tell what I am doing wrong here?
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