[BioC] MAplot (AffyPLM) using an AffyBatch object

[Javier Pérez Florido]

Hi everyone,
I'm new in this Bioconductor project so I hope you help me guys!
I'm using the MAplot funcion (AffyPLM package) with an AffyBatch object 
and when the number of reference arrays is greater than 1, the R console 
gives the following warning:

    In if (i != ref) { :
      the condition has a lengt >1 and the first element will be used

The MA plots are painted, but I don't know if the calculations inside 
the MAplot function are performed well. If the object is an expression 
set, there are no warnings.

Any tips??
Thanks in advance,
Javier