[BioC] RNA degradation plot

[Bill Kenworthy]

Using the affy library, I did an RNA degradation plot for 5 mu74Av2
mouse chips and it generated the figures below.  I do not have anything
to measure this against - if someone has some figures on what "degraded"
RNA looks like (and/or some thresholds), and a representative plot I
would be appreciative.

slope -0.0201 -0.236 -0.228 -0.0884 -0.209
pvalue 0.858 0.0517 0.0751 0.44 0.115

Thanks
BillK