[BioC] spot filtering

michael watson (IAH-C) michael.watson at bbsrc.ac.uk
Fri Jul 22 19:00:43 CEST 2005

Actually, I don't use any of the bioconductor functions for reading in flags or weighting values depending on quality of the spot etc.

Generally, what I do is create a table of flags - with spots as the rows and array as the column.  These flags are sometimes genepix flags, sometimes composite flags I made up.

Then I do all of my analysis in limma, using all data, I don't weight anything, and I don't convert anything into NAs.

At the end, I output the data from topTable() into a text file, load it into MySQL or MS Access, link it to the flags data and decide which, out of my list from topTable, I believe according to the flags.

Note you *could* do this linking in R using the merge() function too.

-----Original Message-----
From:	Brooke-Powell, Elizabeth [mailto:etbp2 at borcim.wustl.edu]
Sent:	Fri 22/07/2005 5:41 PM
To:	bioconductor at stat.math.ethz.ch
Cc:	michael watson (IAH-C)
Subject:	spot filtering


I was interested in how you flag your data, when you load your files do you
read in your flag column as part of a standard GenePix type output file, so
limma uses it when the linear model is fit? I use BlueFuse and its flag
column is quite different from GenePix and the like and at present not able
to be used in limma. I am wondering how to mark (flag) the bad data and
either leave it in or what to put in the data file to get the data ignored
i.e. can you put NA in place of the data point and have it ignored? Is it as
simple as creating a new flag column converting the BlueFuse flags into
GenePix like flags? If I load the data file using the other file type option
in LimmaGUI it doesn't allow me to tell it where there is a flag column. Is
this something that could be fixed assuming the flag column conforms to the
GenePix style of 0, +1 and -1 calls?

Thanks for the help and insight,



Message: 12
Date: Thu, 21 Jul 2005 10:56:09 +0100
From: "michael watson \(IAH-C\)" <	>
Subject: Re: [BioC] Gene filtering for differential expression (limma)
To: "Spela Baebler" <Spela.Baebler at nib.si>
Cc: bioconductor at stat.math.ethz.ch
<8975119BCD0AC5419D61A9CF1A923E950172DA58 at iahce2knas1.iah.bbsrc.reserved>
Content-Type: text/plain;	charset="us-ascii"

Gordon's right, if you post an example of your targets file we will have
a better idea of what you mean

>>Initial quality control and
>>spot filtering are performed in image analysis program.

Personally, I wouldn't recommend doing this.  The way R works, it's
better to have all your data points present in all files.  I leave all
data in and flag up bad spots, and remove them at the end of the
analysis, not the beginning


More information about the Bioconductor mailing list