I don't think that'll work, Friedrich, since Wanli says the variable names are the same in both files. Now if he (perhaps a she -- je ne sais pas) knows that each data set has the same ten variables & each has N observations, then something like this would be possible:
use dataset1.dta, clear
append datatset2.dta
foreach var of varlist ....{
replace `var' = `var' - `var'[_n - N] if _n > N
}
Or to put it more concretely in terms of an example, assume dataset1 has variables x & y & dataset2 the same variables; each has four observations. After appending,
+-------+
| x y |
|-------|
| 1 2 |
| 2 3 |
| 3 4 |
| 4 5 |
| 1 2 |
|-------|
| 2 3 |
| 3 3 |
| 4 5 |
+-------+
. foreach var of varlist x y {
2. replace `var' = `var' - `var'[_n - 4] if _n > 4
3. }
(4 real changes made)
(4 real changes made)
. l, noobs
+--------+
| x y |
|--------|
| 1 2 |
| 2 3 |
| 3 4 |
| 4 5 |
| 0 0 |
|--------|
| 0 0 |
| 0 -1 |
| 0 0 |
+--------+
If the data sets were identical, observations 5-8 would contain all zeros -- not the case here. I haven't given any thought to string variables, but undoubtedly something quasi-similar could be done for them.
Hope this helps,
Eric
>Wanli,
>
>Rename the variables in one file, merge the data and then calculate
>the difference.
>
>Friedrich Huebler
>
>--- Wanli Zhao <[email protected]> wrote:
>> I have 2 datasets. Each one has 10 variables and they share the
>> same names
>> across the 2 data files. Is there a quick way to generate the third
>> file
>> which has the differenced values for each variables in the 2
>> original files?
>> Thanks.
>>
>> Cheers,
>> Wanli
>
>
>
>
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