Dear Bioconductor list,

I am using edgeR to test for differential expression but I also I would
like to know how to test whether expression variability (per gene) is
significantly different between biological groups or treatments.

For instance, the next is my experimental design, according to which I have
two treatments (Hot and Cold) and two biological groups (Hot Adapted and
Cold adapted; two replicates each).

$samples
                 group lib.size norm.factors
R4.Hot     HotAdaptedHot 17409289    0.9881635
R5.Hot     HotAdaptedHot 17642552    1.0818144
R9.Hot    ColdAdaptedHot 20010974    0.8621807
R10.Hot   ColdAdaptedHot 14064143    0.8932791
R4.Cold   HotAdaptedCold 11968317    1.0061084
R5.Cold   HotAdaptedCold 11072832    1.0523857
R9.Cold  ColdAdaptedCold 22386103    1.0520949
R10.Cold ColdAdaptedCold 17408532    1.0903311


I would like to detect those genes for which the expression variability
between R4.Hot and R5.Hot is significantly different to that obtained for
R4.Cold and R5.Cold. Can I use the tagwise dispersion values provided by
edgeR, and how??

Many thanks!
Miguel

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