\name{warpSet}
\alias{warpSet}

\title{Normalization based on landmark registration}

\description{

  This function will perform a normalization of flow cytometry
  data based on warping functions computed on high-density region
  landmarks for individual flow channels.
  
}

\usage{
warpSet(x, stains, grouping = NULL, monwrd = TRUE, subsample=NULL,
peakNr=NULL, clipRange=0.01, nbreaks=11, fres, warpFuns=FALSE, ...)
}


\arguments{
  
  \item{x}{ A \code{\link[flowCore:flowSet-class]{flowSet}}. }
  
  \item{stains}{ A character vector of flow parameters in \code{x} to be
    normalized. }
  
  \item{grouping}{ A character indicating one of the phenotypic
    variables in the \code{phenoData} slot of \code{x} used as a grouping
    factor. The within-group and between-group variance is computed and
    a warning is issued in case the latter is bigger than the former,
    indicating the likely removal of signal by the normalization
    procedure.  }

  \item{monwrd}{ Logical. Compute strictly monotone warping
    functions. This gets directly passed on to
    \code{\link[fda]{landmarkreg}}. }

  \item{subsample}{ Numeric. Reduce the number of events in each \code{flowSet}
    by sub sampling for all density estimation steps and the calculation
    of the warping functions. This can increase computation time for
    large data sets, however it might reduce the accuracy of the density
    estimates. To be used with care. }

  \item{peakNr}{ Numeric scalar. Force a fixed number of peaks to use
    for the normalization.}

  \item{clipRange}{Only use peaks within a clipped data
    range. Essentially, the number indicates the percent of clipping on
    both sides of the data range, e.g. \code{min(x) - 0.01 *
      diff(range(x))}.}

  \item{nbreaks}{The number of spline sections used to approximate the
    data. Higher values produce more accurate results, however this
    comes with the cost of increaseqd computing times. For most data,
    the default setting is good enough.}

  \item{fres}{A named list of \code{filterResultList} objects. This can
    be used to speed up the process since the \code{curv1Filter} step
    can take quite some time.}
  
  \item{warpFuns}{Logical indcating whether to return the normalized
    \code{flowSet} or a list of warping functions.}
  
  \item{\dots}{ Further arguments that are passed on to
    \code{landmarkreg}. }
  
}

\details{

  Normalization is achived by first identifying high-density regions
  (landmarks) for each \code{\link[flowCore:flowFrame-class]{flowFrame}}
  in the \code{flowSet} for a single channel and subsequently by
  computing warping functions for each \code{flowFrame} that best align
  these landmarks. This is based on the algorithm implemented in the
  \code{landmarkreg} function in the \code{\link[fda:fda-package]{fda}}
  package. An intermediate step classifies the high-density regions, see
  \code{\link{landmarkMatrix}} for details.

  Please note that this normalization is on a channel-by-channel
  basis. Multiple channels are normalized in a loop.  
  
  
}


\value{

  The normalized \code{flowSet} if \code{warpFuns} is \code{FALSE},
  otherwise a list of warping functions. Additional inforamtion is
  attached as the \code{warping} attribute to the \code{flowSet} in form
  of a list.
  
}

\references{
  
 J.O. Ramsay and B.W. Silverman: Applied Functional Data Analysis,
 Springer 2002

}


\author{ Florian Hahne }

\note{

  We currently use a patched fda version.
  
}

\seealso{

  \code{\link[flowCore:curv1Filter-class]{curv1Filter}},
  \code{\link{landmarkMatrix}}
  
}

\examples{

data(ITN)
dat <- transform(ITN, "CD4"=asinh(CD4), "CD3"=asinh(CD3), "CD8"=asinh(CD8))
lg <- lymphGate(dat, channels=c("CD3", "SSC"),
preselection="CD4",scale=1.5)
dat <- Subset(dat, lg$n2gate)
datr <- warpSet(dat, "CD8", grouping="GroupID", monwrd=TRUE)
if(require(flowViz)){
d1 <- densityplot(~CD8, dat, main="original", filter=curv1Filter("CD8"))
d2 <- densityplot(~CD8, datr, main="normalized", filter=curv1Filter("CD8"))
plot(d1, split=c(1,1,2,1))
plot(d2, split=c(2,1,2,1), newpage=FALSE)
}

}