[BioC] data reduction in "hist" function?

[Hinnerk Boriss]

Hi all!

Can someone explain to my why the hist function applied to the
expression values returns less values, i.e. less genes, than there are
on the hu68 chip?  

Here my code fragments:

> Mydata <- ReadAffy(CDFfile="hu6800.cdf",...)
> Mydata.rma <- express(Mydata)
> dim(exprs(Mydata.rma))
[1] 7129   18
# ok, here we have 7129 expression values

> Mydata.rma.hist <- hist(exprs(Mydata.rma),,plot=F)
> sum(Mydata.rma.hist$counts)
[1] 42774
# here we are down to 42774 genes

Cheers,
Hinnerk