[BioC] how to normalize by columns

[diego huck]

Hello

  I am a beginner at bioconductor and R. I have a confussion about how 
to do a normalization which consist of obtain the mean of a column, and 
then substract the mean of the column to each value in the column.
  x1(1)- mean(col x1)	x2(1)- mean(col x2)
  x1(2)- mean(col x1)	x2(2)- mean(col x2)
  x1(3)- mean(col x1)	x2(3)- mean(col x2)
....................	...................


  I have the genes in columns and the conditions in rows.
  I don't want to stabilize the variance.
  As you can see is a very simple calculation.
  I am wondering if could use packages like vsn or affy to do that or is 
more easy to write a script.
  Futhermore, I have a doubt if such simple normalization is 
conceptually correct whith the objetive of eliminate the effect between 
array.
  I would to know if I have to iterate any numbers of times the process 
o f calculate the mean of each column and substract the mean.

Thank you

diego lugro
studient
universidad de buenos aires
argentina