Hi Yupu.

I haven't explored this in any detail, but on a cursory inspection (below), it appears that biomaRt has 244000 probesets represented in its database (which seems about right).

> bm <- getBM (attributes = c ("affy_huex_1_0_st_v2 ","hgnc_symbol","chromosome_name","band"),mart=mart)
> dim(bm)
[1] 324334      4
> head(bm)
  affy_huex_1_0_st_v2 hgnc_symbol chromosome_name   band
1             3581777       IGHA2              14 q32.33
2             3581646       IGHA2              14 q32.33
3             3581642       IGHA2              14 q32.33
4             3581781       IGHA2              14 q32.33
5             3581783       IGHA2              14 q32.33
6             3581788       IGHA2              14 q32.33
> length(unique(bm$affy_huex_1_0_st_v2))
[1] 244801

Strictly speaking, this isn't an aroma.affymetrix question. What I suggest you try is exploring what identifiers are not represented in the database and whether something is missing from biomaRt (or the Ensembl web page).

Of course, you can also get annotation from other sources (e.g. from Affymetrix).

Hope that helps,
Mark


On 7-Jan-10, at 7:30 AM, yupu wrote:

Hi,

I am new to exon array analysis. I managed to follow the instructions
from 
http://groups.google.com/group/aroma-affymetrix/web/human-exon-array-analysis
to get the estimation of transcript:

trFit <- extractDataFrame(cesTr, units=1:3, addNames=TRUE)

Then I followed the following thread's idea of using biomaRt to get
the annotation information through the group id of trFit object:
http://groups.google.com/group/aroma-affymetrix/browse_thread/thread/1f4af7fca4352022/a3fe6980ffa7b925?lnk=gst&q=questions+about+annotations#a3fe6980ffa7b925

groupnames = trFit[,2]

ann<-getBM(attributes = c("affy_huex_1_0_st_v2", "hgnc_symbol"),
filters = "affy_huex_1_0_st_v2", values = groupnames, mart = ensembl)

What surprised me is a majority of these group ids don't have any gene
symbol or refseq id associated with them (even I was using the core
probeset upstream)

length(groupnames)
[1] 18708

dim(ann)
[1] 7835    2

I am not sure if this is expected or I am doing something wrong here.

Thanks,
Yupu


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------------------------------
Mark Robinson, PhD (Melb)
Epigenetics Laboratory, Garvan
Bioinformatics Division, WEHI
e: m.robin...@garvan.org.au
e: mrobin...@wehi.edu.au
p: +61 (0)3 9345 2628
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