\HeaderA{normalize.AffyBatch.vsn}{Wrapper for vsn to be used as a normalization method with expresso}{normalize.AffyBatch.vsn}
\begin{Description}\relax
Wrapper for \code{\LinkA{vsn2}{vsn2}} to be used as a normalization
method with the expresso function of the package affy. The expresso
function is deprecated, consider using \code{\LinkA{justvsn}{justvsn}}
instead. The normalize.AffyBatch.vsn can still be useful on its own,
as it provides some additional control of the normalization process
(fitting on subsets, alternate transform parameters).
\end{Description}
\begin{Usage}
\begin{verbatim}normalize.AffyBatch.vsn(abatch, reference, strata=NULL,
  subsample=30000L, subset, log2scale=TRUE, log2asymp=FALSE, ...)\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{abatch}] An object of type
\code{\LinkA{AffyBatch}{AffyBatch}}.
\item[\code{reference}] Optional, a 'vsn' object from a previous fit. If this
argument is specified, the data in 'x' are normalized "towards" an
existing set of reference arrays whose parameters are stored in the
object 'reference'. If this argument is not specified, then the data
in 'x' are normalized "among themselves". See  \code{\LinkA{vsn2}{vsn2}}
for details.
\item[\code{strata}] The 'strata' functionality is not supported, the
parameter is ignored.
\item[\code{subsample}] Is passed on to \code{\LinkA{vsn2}{vsn2}}.
\item[\code{subset}] This allows the specification of a subset of expression
measurements to be used for the vsn fit. The transformation with the
parameters of this fit is then, however, applied to the whole
dataset. This is useful for excluding expression measurements that
are known to be differentially expressed or control probes that may
not match the vsn model, thus avoiding that they influence the
normalization process. This operates at the level of probesets, not
probes. Both 'subset' and 'subsample' can be used together.
\item[\code{log2scale}] If TRUE, this will perform a global affine transform on
the data to put them on a similar scale as the original
non-transformed data. Many users prefer this.  Fold-change estimates
are not affected by this transform. In some situations,
however, it may be helpful to turn this off, e.g., when comparing
independently normalized subsets of the data.
\item[\code{log2asymp}] If TRUE, this will perform a global affine transform on
the data to make the generalized log (asinh) transform be
asymptotically identical to a log base 2 transform. Some people find
this helpful. Only \bold{one} of 'log2scale' or 'log2asymp' can be
set to TRUE. Fold-change estimates are not affected by this
transform.
\item[\code{...}] Further parameters for \code{\LinkA{vsn2}{vsn2}}.
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
Please refer to the \emph{Details} and \emph{References}
sections of the
man page for \code{\LinkA{vsn2}{vsn2}} for more details about this method.

\bold{Important note}: after calling \code{\LinkA{vsn2}{vsn2}}, the function
\code{normalize.AffyBatch.vsn} \bold{exponentiates} the data (base 2).
This is done in order to make the behavior of this function similar to the
other normalization methods in affy. That packages uses the convention
of taking the logarithm to base in
subsequent analysis steps (e.g. in \code{\LinkA{medpolish}{medpolish}}).
\end{Details}
\begin{Value}
An object of class \code{\LinkA{AffyBatch}{AffyBatch}}.
The \code{vsn} object returned, which can be used as \code{reference} for
subsequent fits, is provided by
\code{description(abatch)@preprocessing\$vsnReference}.
\end{Value}
\begin{Author}\relax
D. P. Kreil \url{http://bioinf.boku.ac.at/},
Wolfgang Huber \url{http://www.ebi.ac.uk/huber}
\end{Author}
\begin{SeeAlso}\relax
\code{\LinkA{vsn2}{vsn2}}
\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
## Please see vignette.
\end{ExampleCode}
\end{Examples}

