I have two files, In File1 there are Gene Interactions (Gene Symbol) and the other File2 has the Gene Symbol and its corresponding Ensembl ID.
GeneA GeneB GeneA GeneD GeneC GeneB
GeneA Ensembl1 GeneB Ensembl2 GeneC Ensembl3
Now I want a file which has the output like this File3
GeneA Ensembl1 GeneB Ensembl2 GeneA Ensembl1 GeneD NA GeneC Ensembl3 GeneB Ensembl2
If you notice there was no GeneD in File2 and so when no Ensembl ID was found for this gene, NA was entered against it. Can anybody help me achieve it?