\name{plotTR}
\alias{plotTR}

\title{Plot Trend Effects for LLRA
}
\description{
Plots trend effects over time.  
}
\usage{
plotTR(object, ...)
}
\arguments{
  \item{object}{an object of class \code{"llra"}
}
  \item{\dots}{Additional parameters to be passed to and from other methods}
}
\details{
 The plot is a lattice plot with one panel. The effects for each items
 are plotted over the different time points.
 
  Please
  note that all effects are to be interpreted relative to the baseline
  (i.e. t1).

  Currently, this function only works for a full item x treatment x
  timepoints LLRA. Collapsed effects will not be displayed properly. 
}
\author{
Thomas Rusch
}
\seealso{
  The plot method for treatment effects \code{"plotGR"}.
}
\section{Warning:}{
  Objects of class \code{"llra"} that contain estimates from a collapsed
  data matrix will not be displayed correctly.
}
\examples{
    ##Example 6 from Hatzinger & Rusch (2009)
    groups <- c(rep("TG",30),rep("CG",30))
    llra1 <- LLRA(llradat3,mpoints=2,groups=groups)
    summary(llra1)
    plotTR(llra1)

    ##An LLRA with 2 treatment groups and 1 baseline group, 5 items and 4
    ##time points. Item 1 is dichotomous, all others have 3, 4, 5, 6
    ##categories respectively.
   \dontrun{ 
    ex2 <- LLRA(llraDat2[1:20],mpoints=4,groups=llraDat2[21])
    plotTR(ex2)
 }
}