[BioC] Sample names with ExprSet

[cmprobst]

Dear all,

This a very simple question: 

I am using affy to analyze some arrays, and I want to do mva plots.

I am trying to change the hybridizations names in the first row of the
exprSet, as I dont want to plot the PATH to my CEL files, but just a
legend.

I have tried to change these names by accessing the elements of the
first row in the exprset, but I dont get them.

>exprs(L3hRMA)[0,]
     /home/Genechip/LA_03h_02.CEL /home/Genechip/LA_03h_CBA3_01.CEL
     /home/Genechip/LM_03h_02.CEL /home/Genechip/LM_03h_CBA3_01.CEL
     /home/Genechip/MF_03h_02.CEL /home/Genechip/MF_03h_CBA3_01.CEL

> exprs(L3hRMA)[0,1]
numeric(0)


So, what is missing?

TIA 

Christian