Inter-conversion between EntrezGene ID and Symbols

Code

library (org.Hs.eg.db)

Ann_eg2sy.chv <- unlist (as.list (org.Hs.egSYMBOL))

Ann_sy2eg.chv <- names (Ann_eg2sy.chv)
names (Ann_sy2eg.chv) <- Ann_eg2sy.chv 

# EXAMPLES

# From EntrezGene-ID to Symbol
Ann_eg2sy.chv["100033460"]

# From Symbol to EntrezGene-ID
Ann_sy2eg.chv["SNORD115-20"]

Note:

use org.Xx.eg.db where Xx is the species identifier (e.g. Hs for human, Mm for mouse)
there's lots of of annotation data available in these packages; use ls ("package:ppp.db") to see the, where ppp.db is the package name, e.g. org.Hs.eg.db