[BioC] M vs A plot

[Richard Friedman]

Dear Bioconductors,

	I have normalized a series of arrays using print-tip normalization.
Where as the systematic error in the unnormalized data was pronounced,
The systematic error on the normalized array was reduced greatly.
The M vs. A curve was flat for most of the 48 print-tips. However for a 
few
printips, for A>12 M deviates from close to zero. in one case, M rises 
as high
as M=1/2. at A=15. This only involves a small fraction of the spots (It 
is hard to
estimate what proportion).

	Does this sound serious?

	If so, what should I do about it?

	Is anyone willing to look at the JPEg file (I did not attach it 
because I don't
know if I am allowed to do so).

Thanks and best wishes,
Rich
------------------------------------------------------------
Richard A. Friedman, PhD
Associate Research Scientist
Herbert Irving Comprehensive Cancer Center
Oncoinformatics Core
Lecturer
Department of Biomedical Informatics
Box 95, Room 130BB or P&S 1-420C
Columbia University Medical Center
630 W. 168th St.
New York, NY 10032
(212)305-6901 (5-6901) (voice)
friedman at cancercenter.columbia.edu
http://cancercenter.columbia.edu/~friedman/

"Spring, Summer, and Winter.
Then Fall came along,
and that's the end of our song,
and the pigeons never hibernate at all".
-Rose Friedman, age 7
(These are the correct lyrics and supersede
the version previously at the end of my sig)