[BioC] Obtain MAS5.0 Signal using affy
Kenny Ye
kye@ams.sunysb.edu
Wed, 16 Oct 2002 13:17:49 -0400 (EDT)
Ben and Julien, thanks for pointing me to this document. glad that they
removed it from ``confidential''.
Kenny
Kenny Ye
Assistant Professor
Department of Applied Math and Statistics
SUNY at Stony Brook
Stony Brook, New York 11794-3600
Phone (631)632-9344
Fax (631)632-8490
On 16 Oct 2002, Ben Bolstad wrote:
> You can find a full description of MAS5.0 (or at least the most complete
> I have seen) at
>
> http://www.affymetrix.com/support/technical/whitepapers/sadd_whitepaper.pdf
>
> Ben
>
>
> > Kenny:
> >
> > A full description of the algorithm has been released by Affymetrix. I have
> > a perl version of MAS 5.0 and I will make it available as soon as Affymetrix
> > agrees to it.
> >
> > Regards,
> >
> > Isaac
> >
> > Ye wrote:
> >
> > > has anyone wrote a function for the MAS5.0 signal measure in affy? I am
> > > processing DAT files of some customized chips, and couldn't find the CIF
> > > file that MAS requires. As the CDF file is available, I am able to process
> > > DAT files and obtain CEL files using dChip, then import everything to
> > > affy. Interesting how dChip does it without the CIF file but MAS insists
> > > on it.
> > >
> > > I looked at Hubbell's powerpoint file on Terry's website, but the
> > > equations given there are quite confusing. It shouldn't be difficult to
> > > write the function as long as the formulae are set straight. following is
> > > my best guess
> > >
> > > Signal = Average of Tukey_Biweight(log(PM-CT))
> > >
> > > if MM < PM, CT=MM
> > > if MM > PM, CT=PM/exp(proportion)
> > >
> > > proportion = Average of Tukey_Biweight(log(PM/MM)) (over all pairs
> > > on the chip or just the set?). proportion is set to be 0 if the
> > > average is negative.
> > >
> > > However, one still need to decide the support of the Tukey_Biweight
> > > function. Maybe that doesn't matter much. Or simply take the
> > > median. I don't understand why affymetrix doesn't want to disclose
> > > their algorithm completely.
> > >
> > > Thanks in advance for your suggestions.
> > >
> > > Kenny
> > >
> > > Kenny Ye
> > > Assistant Professor
> > > Department of Applied Math and Statistics
> > > SUNY at Stony Brook
> > > Stony Brook, New York 11794-3600
> > > Phone (631)632-9344
> > > Fax (631)632-8490
> > >
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