
Dear list,
>I have a question about the selection of Variables in dataframes.
>I have a dataframes like this:
>
>CFISCA                FIRMS        YEAR           VAR        VALUE
>20345                     nike            2005            EC01         34
>20345                     nike            2006           EC01         45
>56779                    mediaset   2005           EC01         65
>64568                   agazzini     2005           EC01         78
>64568                    agazzini    2006        EC01           56
>78907                 uniteam       2006       EC01          46
>
>
>what my result should be is a new dataframes which have only firms which have 
>data in both years (2005,2006)
>
>CFISCA       FIRMS    YEAR       VAR    VALUE
>20345          nike         2005       EC01        34
>20345          nike        2006      EC01         45
>64568        agazzini  2005      EC01         78
>64568      agazzini    2006     EC01         56
>
>
>Thanks for your attention!!!




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