I'm trying to annotate gene symbols next to probe IDs (Affymetrix Mouse Gene 1.0-ST Array).
I used "mogene10sttranscriptcluster.db" package (v8.7.0) of R for the annotation.
But here's the problem.
1) Using mogene10sttranscriptcluster.db directly
library(mogene10sttranscriptcluster.db) a <- contents(mogene10sttranscriptclusterSYMBOL) # a$'10344741' #  NA
2) Using AnnotationDbi to extract the info
library(mogene10sttranscriptcluster.db) library(AnnotationDbi) k <- keys(mogene10sttranscriptcluster.db, keytype = "PROBEID") b <- mapIds(mogene10sttranscriptcluster.db, keys=k, column=c("SYMBOL"), keytype="PROBEID") b["10344741"] # 10344741 # "Hnrnpa3" length(a) = length(b) = 35556
But there are some symbols not in the (1) but in the (2).
They both used the same database - mogene10sttranscriptcluster.db, but how did they get different results?
Does the AnnotationDbi converts probe ids to some other ids and then convert them to gene symbols?
The second one seems to have more symbols, so that's the one I have to use?
I'm very confused right now.