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\newcommand{\R}{\texttt{R}}
\newcommand{\pkgname}{\texttt{fastJT}}
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\begin{document}
<<setup1, include=FALSE>>=
require(knitr)
@

<<setup2, include=FALSE>>=
options(width=80)  # make the printing fit on the page
set.seed(1121)     # make the results repeatable
stdt<-date()
@

\begin{frame}
	\title{\pkgname}
	\subtitle{Efficient Jonckheere-Terpstra Test Statistics for Robust Machine Learning and Genome-Wide Association Studies}
	\date{2025-05-01}
	\titlepage
\end{frame}


\begin{frame}{Outline}
	\tableofcontents[]
\end{frame}


\section{Introduction}
\begin{frame}{Introduction}
  \begin{itemize}
    \item This document provides an example for using the \pkgname{} package to calculate the Jonckheere-Terpstra test statistics for large data sets (multiple dependent and independent variables) commonly encountered in machine learning or GWAS. The functionality is also included to perform k-fold cross validation or feature sets.
    \item The calculation of the standardized test statistic employs the null variance equation as defined by \citet[eq. 6.19]{HollanderBook} to account for ties in the data.
    \item The major algorithm in this package is written in C++, which is ported to \R{} by \Rcpp{}, to facilitate fast computation. 
	\item Features of this package include:
      \begin{enumerate}
        \item $O(N\times\log(N))$ computational complexity (where $N$ is the number of the samples)
        \item \openmp{} supported parallelization
        \item Customized output of top $m$ significant independent variables for each dependent variable
      \end{enumerate}
  \end{itemize}
\end{frame}

\begin{frame}[fragile]{fastJT}
<<fastJT, eval=FALSE>>=
res <- fastJT(Y, X, outTopN=15, numThreads=1, standardized=TRUE)
@
Function arguments:\\
\begin{description}
	\item[\texttt{Y}:] Matrix of continuous values, representing dependent variables, with sample IDs as row names and variable names as column names.
	\item[\texttt{X}:] A matrix of integer values, representing independent variables, with sample IDs as row names and feature IDs as column names.
	\item[\texttt{outTopN}:] Number of top statistics to return (i.e., the largest standardized statistics). The default value is 15. If \texttt{outTopN} is set to \texttt{NA}, all results will be returned.
	\item[\texttt{numThreads}:] Number of threads to use for parallel computation. The default value is 1 (sequential computation).
	\item[\texttt{standardized}:] A boolean to specify whether to return standardized statistics or non-standardized statistics. The default value is \texttt{TRUE}, returning standardized statistics.
\end{description}
Users may wish to consider the \texttt{dplyr::recode()} function for converting non-numeric group indices into ordinal values for argument \texttt{X}.
\end{frame}

\begin{frame}[fragile]{Returned Values}
Function returns:
\begin{description}
 	\item[\texttt{J}:] A matrix of standardized/non-standardized Jonckheere-Terpstra test statistics, depending on option \texttt{standardized}, with column names from input \texttt{Y}. If \texttt{outTopN} is not \texttt{NA}, results are sorted within each column.
	\item[\texttt{XIDs}:] If \texttt{outTopN} is not \texttt{NA}, this is a matrix of column names from \texttt{X} associated with top standardized Jonckheere-Terpstra test statistics from \texttt{J}. Otherwise this is an unsorted vector of column names from input \texttt{X}.
\end{description}
\end{frame}


\begin{frame}[fragile]{fastJT.select}
<<fastJTselect, eval=FALSE>>=
res <- fastJT.select(Y, X, cvMesh=NULL, kFold=10L,
                     selCrit=NULL, outTopN=15L, numThreads=1L)
@
Function arguments:\\
\begin{description}
        \item[\texttt{Y}:] Matrix of continuous values, representing dependent variables, with sample IDs as row names and variable names as column names.
        \item[\texttt{X}:] Matrix of integer values, representing independent variables, with sample IDs as row names and feature IDs as column names.
        \item[\texttt{cvMesh}:] A user-defined function to specify how to separate the data into training and testing parts. The inputs of this function are a vector of the sample IDs and \texttt{kFold}, an integer representing the number of folds for cross validation. The output of this function is a list of \texttt{kFold} vectors of sample IDs forming the testing subset for each fold. The default value is \texttt{NULL}, and if no function is specified, the data are partitioned sequentially into \texttt{kFold} equal sized subsets. Optional.
\end{description}
\end{frame}

\begin{frame}[fragile]{fastJT.select}
Function arguments continued:\\
\begin{description}
        \item[\texttt{kFold}:] An integer to indicate the number of folds. Optional. The default value is 10.
        \item[\texttt{selCrit}:] A user-defined function to specify the criteria for selecting the top features. The inputs of this function include \texttt{J}, the matrix of statistics resulting from \texttt{fastJT}, and \texttt{P}, the matrix of p-values from \texttt{pvalues(J)}. The output is a data frame containing the selected feature IDs for each trait of interest. Optional. The default value is \texttt{NULL}, and if no function is specified, the features the largest standardized Jonckheere-Terpstra test statistics are selected.
        \item[\texttt{outTopN}:] An integer to indicate the number of top hits to be returned when \texttt{selCrit=NULL}. Unused if \texttt{selCrit!=NULL}. Optional. The default value is 15.
        \item[\texttt{numThreads}:] A integer to indicate the number of threads to be used in the computation. Optional. The default value is 1 (sequential computation).
\end{description}
The function withholds one subset while the remaining \texttt{kFold}-1 subsets are used to test the features. The process is repeated \texttt{kFold} times, with each of the subsets withheld exactly once as the validation data.
\end{frame}



\begin{frame}[fragile]{Returned Values}
Function returns: Three \texttt{lists} of length \texttt{kFold}:
\begin{description}
        \item[\texttt{J}:] A \texttt{list} of matrices of standardized Jonckheere-Terpstra test statistics, one for each  cross validation.
        \item[\texttt{Pval}:] A \texttt{list} of matrices of p-values, one for each cross validation.
        \item[\texttt{XIDs}:] A \texttt{list} of matrices of the selected feature IDs, one for each cross validation.
\end{description}
\end{frame}


\section{Examples}
\begin{frame}[fragile]{Simulate Data}
  \begin{enumerate}
  \item Define the number of markers, samples, and features:
<<inputPara>>=
num_sample	<- 100
num_marker 	<- 4
num_feature 	<- 50
@  
\item Create two matrices containing marker levels and feature information.
  \begin{enumerate}
    \item \texttt{Data} contains the samples' marker levels.
    \item \texttt{Feature} contains the samples' feature values.
  \end{enumerate}	

<<markers_levels_geno_types>>=
set.seed(12345);
Data    <- matrix(rnorm(num_sample*num_marker), 
                  num_sample, num_marker)
Feature <- matrix(rbinom(num_sample*num_feature,2,0.5),
                  num_sample, num_feature)
colnames(Data)    <- paste0("Mrk:",1:num_marker)
colnames(Feature) <- paste0("Ftr:",1:num_feature)
@ 
  \end{enumerate}
\end{frame}


\begin{frame}[fragile]{Load Package}
Load \pkgname{} (after installing its dependent packages):
<<loadpkg>>=
library(fastJT)
@ 
\end{frame}


\begin{frame}[fragile]{Example Execution}
<<exp3, results='hide'>>=
JTStat <- fastJT(Y=Data, X=Feature, outTopN=10)
summary(JTStat, Y2Print=1:4, X2Print=1:5)
@
<<exp4, echo=FALSE, size='tiny'>>=
summary(JTStat, Y2Print=1:4, X2Print=1:5)
@
\end{frame}

\begin{frame}[fragile]{Example Execution: Statistics in the Summary}
<<exp5, eval=FALSE>>=
summary(JTStat, Y2Print=1:4, X2Print=1:5, printP=FALSE)
@
<<exp6, echo=FALSE, size='tiny'>>=
summary(JTStat, Y2Print=1:4, X2Print=1:5, printP=FALSE)
@
\end{frame}

\begin{frame}[fragile]{Example Execution: Sorting in the Summary}
<<exp7, results='hide'>>=
JTAll <- fastJT(Y=Data, X=Feature, outTopN=NA)
summary(JTAll, Y2Print=1:4, outTopN=3)
@
<<exp8, echo=FALSE, size='tiny'>>=
summary(JTAll, Y2Print=1:4, outTopN=3)
@
\end{frame}


\begin{frame}[fragile]{Example Execution: \texttt{fastJT.select}}
<<select1, eval=FALSE>>=
fastJT.select(Y=Data, X=Feature, cvMesh=NULL, kFold=5,
              selCrit=NULL, outTopN=5, numThreads=1)
@
<<select1out, echo=FALSE, size='tiny'>>=
fastJT.select(Y=Data, X=Feature, cvMesh=NULL, kFold=5,
              selCrit=NULL, outTopN=5, numThreads=1)
@
\end{frame}

\begin{frame}[fragile]{Example User-Defined \texttt{cvMesh} Function}
<<cvMesh, results='hide'>>=
Mesh <- function(rownamesData, kFold){
  numSamples <- length(rownamesData)
  res <- NULL
  subSampleSize <- floor(numSamples/kFold)
  for (i in 1:kFold){
    start <- (i-1)*subSampleSize + 1
    if(i < kFold)
      end <- i*subSampleSize
    else
      end <- numSamples
    if(i == 1)
      res <- list(c(start:end))
    else
      res[[i]] <- c(start:end)
  }
  res
}
@
\end{frame}

\begin{frame}[fragile]{Example User-Defined \texttt{selCrit} Function}
<<selCrit, results='hide'>>=
whichpart <- function(x, n=30) {
  nx <- length(x)
  p <- nx-n
  xp <- sort(x, partial=p)[p]
  which(x > xp)
}

selectCrit <- function(J, P){
  pcut <- 0.95
  hit <- NULL
  for(i in 1:ncol(P)){
    if(i == 1)
      hit <- list(rownames(P)[whichpart(P[,i], 4)])
    else
      hit[[i]] = rownames(P)[whichpart(P[,i], 4)]
  }
  res <- do.call(cbind, hit)
  colnames(res) <- colnames(P)
  res
}
@
\end{frame}

\begin{frame}[fragile]{Example Execution with User-Defined Functions}
<<select2, eval=FALSE>>=
fastJT.select(Data, Feature, cvMesh=Mesh, kFold=5,
              selCrit=selectCrit, outTopN=5, numThreads=1)
@
<<select2out, echo=FALSE, size='tiny'>>=
fastJT.select(Data, Feature, cvMesh=Mesh, kFold=5,
              selCrit=selectCrit, outTopN=5, numThreads=1)
@
\end{frame}


\section*{}
\begin{frame}[fragile]{References}
% {\footnotesize
\begin{thebibliography}{9}
\setbeamertemplate{bibliography item}[text]
\bibitem[Hollander and Wolfe(1999)]{HollanderBook}
	Hollander, M. and Wolfe, D. A.,
	\emph{Nonparametric Statistical Methods}.
        New York, Wiley,
        2nd edition,
	1999.
\end{thebibliography}
% }
\end{frame}


\section{Session Information}
\begin{frame}[fragile]{Session Information}
<<sessinfo, echo=FALSE, include=TRUE, results='asis'>>=
toLatex(sessionInfo(), locale=FALSE)
@ 
<<times, echo=FALSE, include=TRUE>>=
print(paste("Start Time",stdt))
print(paste("End Time  ",date()))
@ 
\end{frame}

\end{document}























