Common elements in columns

Hi,

I have 4 files with 10000 individuals in each file and 10 columns each.
One of the columns, say C1, may have elements in common with the other
columns C1 of other files.

If I have only 2 files, I can do this check with the command:

data1[data1 %in% data2]
data2[data2 %in% data1]

How do I check which common elements in the columns of C1 4 files?

Thanks,

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Silvano Cesar da Costa

Universidade Estadual de Londrina
Centro de Ci?ncias Exatas
Departamento de Estat?stica

Fone: (43) 3371-4346