st: replace values through observations with criterion

["Abssi, Fouad" <fabssi@essex.ac.uk>]

I would like to copy a value of a variable in an observation and replace it to another observation in the same variable with criterion. I am using Stata 12.1 for Windows. I have 1754298 observations, and five variables: reporter, product, year, exporter, and tariff ON tariff data. My data looks like this.

Reporter        Product         Partner                 Year            Tariff
GERMANY 111             Australia       1992            .
GERMANY 111             Australia       1993            4.36
GERMANY 111             Canada  1995            7.01
GERMANY 123             Canada  1992            0
GERMANY 123             Canada  1995            5
GERMANY 251             Chile   1993            2.81
UK      111             Australia       1992            3.2
UK      111             Australia       1993            3.75
UK      111             Canada  1995            7
UK      123             Canada  1992            5.94
UK      123             Canada  1995            5.48
UK      251             Chile   1993            4.29
USA     111             Australia       1992            0
USA     111             Australia       1993            4
USA     111             Canada  1995            5
USA     123             Canada  1992            2.73
USA     123             Canada  1995            3.62
USA     251             Chile   1993            4.39

I would like to tell Stata to copy tariff value from the observation where UK is Reporter (for example) to the observation where GERMANY is Reporter (for example), and (Product, year, and Partner are the same). Please note that the number of observations is 1754298, and for Reporter and Partner there are 50 countries, for Product there are almost 26 product, for Year there is 18 years.

Many Thanks,
Fouad Abssi

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