Hi, all!

While I was trying to convert Ensembl ID to Entrez ID using 'mapIDs', I noticed number of missing IDs in the result.

18,453 Ensembl IDs were input, but only 18,364 Entrez IDs were returned.

I was expecting the missing IDs would be presented as 'NA' or something like that. Instead, they weren't included in the result at all.

The data I'm trying to convert IDs,

> head(de)
                   p_val avg_logFC pct.1 pct.2 p_val_adj fcsign logP metric
ENSMUSG00000000184     0 1.5573130 0.992 0.016         0      1    0      0
ENSMUSG00000053030     0 1.3555568 1.000 0.005         0      1    0      0
ENSMUSG00000037820     0 1.1589184 0.875 0.009         0      1    0      0
ENSMUSG00000005087     0 0.9234463 0.842 0.002         0      1    0      0
ENSMUSG00000026586     0 0.7931385 0.658 0.000         0      1    0      0
ENSMUSG00000050010     0 0.7784591 0.733 0.000         0      1    0      0

and R code I used,

ranks$entrez = mapIds(org.Mm.eg.db,
                      keys=row.names(de), 
                      column="ENTREZID",
                      keytype="ENSEMBL",
                      multiVals="filter")

What seems to be the problem here?

Please, help me!

Thank you!