ds.contourPlot.R

#'
#' @title Generates a contour plot 
#' @description  It generates a contour plot of the pooled data
#' or one plot for each dataset on the client-side. 
#' @details The \code{ds.contourPlot} function first generates 
#' a density grid and uses it to plot the graph.
#' The cells of the grid density matrix that hold a count of less than the filter set by
#' DataSHIELD (usually 5) are considered invalid and turned into 0 to avoid potential
#' disclosure. A message is printed to inform the user about the number of invalid cells.
#' 
#' The ranges returned by each study and used in the process of getting the grid density matrix
#' are not the exact minimum and maximum values but rather close approximates of the real
#' minimum and maximum value. This was done to reduce the risk of potential disclosure.
#' 
#' In the \code{k} parameter the user can choose any value for \code{k} equal to or greater 
#' than the pre-specified threshold used as a disclosure control for this method 
#' and lower than the number of observations minus the value of this threshold. 
#' \code{k} default value is  3 (we suggest k to be equal to, or bigger than, 3). 
#' Note that the function fails if the user
#' uses the default value but the study has set a bigger threshold. 
#' The value of \code{k} is used only if the argument \code{method} is set to \code{'deterministic'}. 
#' Any value of k is ignored if the
#' argument \code{method} is set to \code{'probabilistic'} or \code{'smallCellsRule'}.
#' 
#' In \code{noise} any value of noise is ignored if
#' the argument \code{method} is set to \code{'deterministic'} or \code{'smallCellsRule'}. The user can choose
#' any value for noise equal to or greater than the pre-specified threshold \code{'nfilter.noise'}.
#' Default noise value is  0.25. 
#' The added noise follows a normal distribution with zero mean and variance equal to a percentage of
#' the initial variance of each input variable.
#' 
#' Server functions called: \code{heatmapPlotDS}, \code{rangeDS} and \code{densityGridDS}
#' 
#' @param x a character string providing the name of a numerical vector.
#' @param y a character string providing the name of a numerical vector.
#' @param type a character string that represents the type of graph to display.
#' If \code{type} is set to \code{'combine'}, a combined contour plot displayed and
#' if \code{type} is set to \code{'split'}, each contour is plotted separately.
#' @param show a character that represents where the plot should focus.
#' If \code{show} is set to \code{'all'}, the ranges of the variables are used as plot limits.
#' If \code{show} is set to \code{'zoomed'}, the plot is zoomed to the region where the actual data are.
#' @param numints number of intervals for a density grid object.
#' @param method a character that defines which contour will be created. If \code{method}
#' is set to \code{'smallCellsRule'} (default), the contour plot of the actual variables is
#' created but grids with low counts are replaced with grids with zero counts. If \code{method} is
#' set to \code{'deterministic'} the contour of the scaled centroids of each k nearest neighbour of the
#' original variables is created, where the value of \code{k} is set by the user. If the
#' \code{method} is set to \code{'probabilistic'}, then the contour of 'noisy' variables is generated. 
#' @param k the number of the nearest neighbours for which their centroid is calculated. For more information
#' see details. 
#' @param noise the percentage of the initial variance that is used as the variance of the embedded
#' noise if the argument \code{method} is set to \code{'probabilistic'}. For more information see details. 
#' @param datasources a list of \code{\link{DSConnection-class}} objects obtained after login. 
#' If the \code{datasources} argument is not specified
#' the default set of connections will be used: see \code{\link{datashield.connections_default}}.
#' @return \code{ds.contourPlot} returns a contour plot to the client-side. 
#' @author DataSHIELD Development Team
#' @examples
#' \dontrun{
#' 
#'   ## Version 6, for version 5 see the Wiki
#'   # Connecting to the Opal servers
#' 
#'   require('DSI')
#'   require('DSOpal')
#'   require('dsBaseClient')
#' 
#'   builder <- DSI::newDSLoginBuilder()
#'   builder$append(server = "study1", 
#'                  url = "http://192.168.56.100:8080/", 
#'                  user = "administrator", password = "datashield_test&", 
#'                  table = "CNSIM.CNSIM1", driver = "OpalDriver")
#'   builder$append(server = "study2", 
#'                  url = "http://192.168.56.100:8080/", 
#'                  user = "administrator", password = "datashield_test&", 
#'                  table = "CNSIM.CNSIM2", driver = "OpalDriver")
#'   builder$append(server = "study3",
#'                  url = "http://192.168.56.100:8080/", 
#'                  user = "administrator", password = "datashield_test&", 
#'                  table = "CNSIM.CNSIM3", driver = "OpalDriver")
#'   logindata <- builder$build()
#'   
#'   # Log onto the remote Opal training servers
#'   connections <- DSI::datashield.login(logins = logindata, assign = TRUE, symbol = "D") 
#'   
#'   # Generating contour plots
#'
#'   ds.contourPlot(x = "D$LAB_TSC",
#'                  y = "D$LAB_HDL",
#'                  type = "combine", 
#'                  show = "all",
#'                  numints = 20,
#'                  method = "smallCellsRule",  
#'                  k = 3, 
#'                  noise = 0.25,
#'                  datasources = connections)
#'
#'   # clear the Datashield R sessions and logout
#'   datashield.logout(connections)
#'
#' }
#' @export
#' 
ds.contourPlot <- function(x=NULL, y=NULL, type='combine', show='all', numints=20, method="smallCellsRule", k=3, noise=0.25, datasources=NULL){

  # look for DS connections
  if(is.null(datasources)){
    datasources <- datashield.connections_find()
  }

  # ensure datasources is a list of DSConnection-class
  if(!(is.list(datasources) && all(unlist(lapply(datasources, function(d) {methods::is(d,"DSConnection")}))))){
    stop("The 'datasources' were expected to be a list of DSConnection-class objects", call.=FALSE)
  }

  if(is.null(x)){
    stop("x=NULL. Please provide the names of two numeric vectors!", call.=FALSE)
  }
  if(is.null(y)){
    stop("y=NULL. Please provide the names of two numeric vectors!", call.=FALSE)
  }
  
  # check if the input objects are defined in all the studies
  isDefined(datasources, x)
  isDefined(datasources, y)

  # call the internal function that checks the input object(s) is(are) of the same class in all studies.
  typ.x <- checkClass(datasources, x)
  typ.y <- checkClass(datasources, y)

  # the input objects must be numeric or integer vectors
  if(!('integer' %in% typ.x) & !('numeric' %in% typ.x)){
    message(paste0(x, " is of type ", typ.x, "!"))
    stop("The input objects must be integer or numeric vectors.", call.=FALSE)
  }
  if(!('integer' %in% typ.y) & !('numeric' %in% typ.y)){
    message(paste0(y, " is of type ", typ.y, "!"))
    stop("The input objects must be integer or numeric vectors.", call.=FALSE)
  }
  
  # the argument method must be either "smallCellsRule" or "deterministic" or "probabilistic"
  if(method != 'smallCellsRule' & method != 'deterministic' & method != 'probabilistic'){
    stop('Function argument "method" has to be either "smallCellsRule" or "deterministic" or "probabilistic"', call.=FALSE)
  }

  # extract the variable names to be used as labels in the plot
  xnames <- extract(x)
  x.lab <- xnames[[length(xnames)]]
  ynames <- extract(y)
  y.lab <- ynames[[length(ynames)]]

  # name of the studies to be used in the plots' titles
  stdnames <- names(datasources)

  # number of studies
  num.sources <- length(datasources)

  # if the method is set to 'deterministic' or 'probabilistic' call the server-side function
  # heatmapPlotDS that generates the anonymous data. NOTE is the same server-side function that
  # is used by the ds.heatmapPlot function
  if (method=="deterministic"){

    method.indicator <- 1

    # call the server-side function that generates the x and y coordinates of the centroids
    cally <- paste0("heatmapPlotDS(", x, ",", y, ",", k, ",", noise, ",", method.indicator, ")")
    anonymous.data <- DSI::datashield.aggregate(datasources, cally)

    pooled.points.x <- c()
    pooled.points.y <- c()
    for (i in 1:num.sources){
      pooled.points.x[[i]] <- anonymous.data[[i]][[1]]
      pooled.points.y[[i]] <- anonymous.data[[i]][[2]]
    }
  }

  if (method=="probabilistic"){

    method.indicator <- 2

    # call the server-side function that generates the x and y coordinates of the anonymous.data
    cally <- paste0("heatmapPlotDS(", x, ",", y, ",", k, ",", noise, ",", method.indicator, ")")
    anonymous.data <- DSI::datashield.aggregate(datasources, cally)

    pooled.points.x <- c()
    pooled.points.y <- c()
    for (i in 1:num.sources){
      pooled.points.x[[i]] <- anonymous.data[[i]][[1]]
      pooled.points.y[[i]] <- anonymous.data[[i]][[2]]
    }
  }

  if(type=="combine"){

    if(method=='smallCellsRule'){

    # get the range from each study and produce the 'global' range
    cally <- paste0("rangeDS(", x, ")")
    x.ranges <- DSI::datashield.aggregate(datasources, as.symbol(cally))

    cally <- paste0("rangeDS(", y, ")")
    y.ranges <- DSI::datashield.aggregate(datasources, as.symbol(cally))

    x.minrs <- c()
    x.maxrs <- c()
    y.minrs <- c()
    y.maxrs <- c()
    for(i in 1:num.sources){
      x.minrs <- append(x.minrs, x.ranges[[i]][1])
      x.maxrs <- append(x.maxrs, x.ranges[[i]][2])
      y.minrs <- append(y.minrs, y.ranges[[i]][1])
      y.maxrs <- append(y.maxrs, y.ranges[[i]][2])
    }
    x.range.arg <- c(min(x.minrs), max(x.maxrs))
    y.range.arg <- c(min(y.minrs), max(y.maxrs))

    x.global.min <- x.range.arg[1]
    x.global.max <- x.range.arg[2]
    y.global.min <- y.range.arg[1]
    y.global.max <- y.range.arg[2]

    # generate the grid density object to plot
    cally <- paste0("densityGridDS(",x,",",y,",",limits=T,",",x.global.min,",",
                    x.global.max,",",y.global.min,",",y.global.max,",",numints, ")")
    grid.density.obj <- DSI::datashield.aggregate(datasources, as.symbol(cally))

    numcol <- dim(grid.density.obj[[1]])[2]

    # print the number of invalid cells in each participating study
    for (i in 1:num.sources) {
      message(stdnames[i],': ', names(dimnames(grid.density.obj[[i]])[2]))
    }

    Global.grid.density <- matrix(0, dim(grid.density.obj[[1]])[1], numcol-2)
    for (i in 1:num.sources){
      Global.grid.density <- Global.grid.density + grid.density.obj[[i]][,1:(numcol-2)]
    }

  }else{

    if (method=="deterministic" | method=="probabilistic"){

        xvect <- unlist(pooled.points.x)
        yvect <- unlist(pooled.points.y)

        # generate the grid density object to plot
        y.min <- min(yvect)
        x.min <- min(xvect)
        y.max <- max(yvect)
        x.max <- max(xvect)

        y.range <- y.max - y.min
        x.range <- x.max - x.min

        y.interval <- y.range / numints
        x.interval <- x.range / numints

        y.cuts <- seq(from = y.min, to = y.max, by = y.interval)
        y.mids <- seq(from = (y.min + y.interval/2), to = (y.max - y.interval/2), by = y.interval)
        y.cuts[numints+1] <- y.cuts[numints+1] * 1.001

        x.cuts <- seq(from = x.min, to = x.max, by = x.interval)
        x.mids <- seq(from = (x.min + x.interval/2), to = (x.max - x.interval/2), by = x.interval)
        x.cuts[numints+1] <- x.cuts[numints+1] * 1.001

        grid.density <- matrix(0, nrow=numints, ncol=numints)

        for(j in 1:numints){
          for(k in 1:numints){
            grid.density[j,k] <- sum(1*(yvect >= y.cuts[k] & yvect < y.cuts[k+1] & xvect >= x.cuts[j] & xvect < x.cuts[j+1]), na.rm=TRUE)
          }
        }
        grid.density.obj <- list()
        grid.density.obj[[1]] <- cbind(grid.density,x.mids,y.mids)

        numcol <- dim(grid.density.obj[[1]])[2]

        Global.grid.density <- grid.density

      }
    }

    # prepare arguments for the plot function
    graphics::par(mfrow=c(1,1))

    x <- grid.density.obj[[1]][,(numcol-1)]
    y <- grid.density.obj[[1]][,(numcol)]
    z <- Global.grid.density

    if (show=='all') {
      # plot a combined contour plot
      graphics::contour(x,y,z, xlab=x.lab, ylab=y.lab, main="Contour Plot of the Pooled Data")
    } else if (show=='zoomed') {

      # find rows and columns on the edge of the grid density object which consist only of zeros and leave only
      # one such row/column on each side
      # rows on the top
      flag <- 0
      rows_top <- 1
      while (flag !=1) {   # find out where non-zero elements start
        if (all(Global.grid.density[rows_top,]==0)) {
          rows_top <- rows_top + 1
        }else{
          flag <- 1
        }
      }
      if (rows_top==1) {  # the first row contains non-zero elements
        dummy_top <- rows_top
      }else{
        dummy_top <- rows_top - 1  # leave one row at the top with only zeros
      }

      # rows at the bottom
      flag <- 0
      rows_bot <- dim(Global.grid.density)[1]
      while (flag !=1) {   # find out where non-zero elements start
        if (all(Global.grid.density[rows_bot,]==0)){
          rows_bot <- rows_bot - 1
        }else{
          flag <- 1
        }
      }
      if (rows_bot==dim(Global.grid.density)[1]) {  # the last row contains non-zero elements
        dummy_bot <- rows_bot
      }else{
        dummy_bot <- rows_bot + 1  # leave one row at the bottom with only zeros
      }

      # columns on the left
      flag <- 0
      col_left <- 1
      while (flag !=1) {   # find out where non-zero elements start
        if (all(Global.grid.density[,col_left]==0)) {
          col_left <- col_left + 1
        }else{
          flag <- 1
        }
      }
      if (col_left==1) {  # the first column contains non-zero elements
        dummy_left <- col_left
      }else{
        dummy_left <- col_left - 1  # leave one column on the left with only zeros
      }

      # columns on the right
      flag <- 0
      col_right <- dim(Global.grid.density)[2]
      while (flag !=1) {   # find out where non-zero elements start
        if (all(Global.grid.density[,col_right]==0)) {
          col_right <- col_right - 1
        }else{
          flag <- 1
        }
      }
      if (col_right==1) {  # the first column contains non-zero elements
        dummy_right <- dim(Global.grid.density)[2]
      }else{
        dummy_right <- col_right + 1  # leave one column on the right with only zeros
      }

      z.zoomed <- Global.grid.density[dummy_top:dummy_bot, dummy_left:dummy_right]
      x.zoomed <- x[dummy_top:dummy_bot]
      y.zoomed <- y[dummy_left:dummy_right]

      # plot a combined contour plot
      graphics::contour(x.zoomed,y.zoomed,z.zoomed, xlab=x.lab, ylab=y.lab, main="Contour Plot of the Pooled Data (zoomed)")
    }else{
      stop('Function argument "show" has to be either "all" or "zoomed"')
    }

  } else if (type=='split') {

   if(method=="smallCellsRule"){
     # generate the grid density object to plot
     num_intervals <- numints
     cally <- paste0("densityGridDS(",x,",",y,",",'limits=FALSE',",",'x.min=NULL',",",
                    'x.max=NULL',",",'y.min=NULL',",",'y.max=NULL',",",numints=num_intervals, ")")
     grid.density.obj <- DSI::datashield.aggregate(datasources, as.symbol(cally))
     numcol <- dim(grid.density.obj[[1]])[2]
   }

   if (method=="deterministic" | method=="probabilistic"){

    grid.density.obj <- list()
    for (i in 1:num.sources){
       xvect <- unlist(anonymous.data[[i]][[1]])
       yvect <- unlist(anonymous.data[[i]][[2]])

       # generate the grid density object to plot
       y.min <- min(yvect)
       x.min <- min(xvect)
       y.max <- max(yvect)
       x.max <- max(xvect)

       y.range <- y.max-y.min
       x.range <- x.max-x.min

       y.interval <- y.range/numints
       x.interval <- x.range/numints

       y.cuts <- seq(from = y.min, to = y.max, by = y.interval)
       y.mids <- seq(from = (y.min + y.interval/2), to = (y.max - y.interval/2), by = y.interval)
       y.cuts[numints+1] <- y.cuts[numints+1] * 1.001

       x.cuts <- seq(from = x.min, to = x.max, by = x.interval)
       x.mids <- seq(from = (x.min + x.interval/2), to = (x.max - x.interval/2), by = x.interval)
       x.cuts[numints+1] <- x.cuts[numints+1] * 1.001

       grid.density <- matrix(0, nrow=numints, ncol=numints)

       for(j in 1:numints){
         for(k in 1:numints){
           grid.density[j,k] <- sum(1*(yvect >= y.cuts[k] & yvect < y.cuts[k+1] & xvect >= x.cuts[j] & xvect < x.cuts[j+1]), na.rm=TRUE)
         }
       }
       grid.density.obj[[i]] <- cbind(grid.density, x.mids, y.mids)

       numcol <- dim(grid.density.obj[[i]])[2]
     }
   }

    # print the number of invalid cells in each participating study
    for (i in 1:num.sources) {
      message(stdnames[i],': ', names(dimnames(grid.density.obj[[i]])[2]))
    }

    if(num.sources > 1){
      if((num.sources %% 2) == 0){ numr <- num.sources/2 }else{ numr <- (num.sources+1)/2}
      numc <- 2
      graphics::par(mfrow=c(numr,numc))
      for(i in 1:num.sources){
        grid <- grid.density.obj[[i]][,1:(numcol-2)]
        x<-grid.density.obj[[i]][,(numcol-1)]
        y<-grid.density.obj[[i]][,(numcol)]
        z<-grid
        title <- paste("Contour Plot of ", stdnames[i], sep="")
        if (show=='all') {
          graphics::contour(x,y,z, xlab=x.lab, ylab=y.lab, main=title)
        } else if (show=='zoomed') {

          # find rows and columns on the edge of the grid density object which consist only of zeros and leave only
          # one such row/column on each side
          # rows on the top
          flag <- 0
          rows_top <- 1
          while (flag !=1) {   # find out where non-zero elements start
            if (all(z[rows_top,]==0)) {
              rows_top <- rows_top+1
            }else{
              flag <- 1
            }
          }
          if (rows_top==1) {  # the first row contains non-zero elements
            dummy_top <- rows_top
          }else{
            dummy_top <- rows_top - 1  # leave one row at the top with only zeros
          }

          # rows at the bottom
          flag <- 0
          rows_bot <- dim(z)[1]
          while (flag !=1) {   # find out where non-zero elements start
            if (all(z[rows_bot,]==0)) {
              rows_bot <- rows_bot - 1
            }else{
              flag <- 1
            }
          }
          if (rows_bot==dim(z)[1]) {  # the last row contains non-zero elements
            dummy_bot <- rows_bot
          }else{
            dummy_bot <- rows_bot + 1  # leave one row at the bottom with only zeros
          }

          # columns on the left
          flag <- 0
          col_left <- 1
          while (flag !=1) {   # find out where non-zero elements start
            if (all(z[,col_left]==0)) {
              col_left <- col_left + 1
            }else{
              flag <- 1
            }
          }
          if (col_left==1) {  # the first column contains non-zero elements
            dummy_left <- col_left
          }else{
            dummy_left <- col_left - 1  # leave one column on the left with only zeros
          }

          # columns on the right
          flag <- 0
          col_right <- dim(z)[2]
          while (flag !=1) {   # find out where non-zero elements start
            if (all(z[,col_right]==0)) {
              col_right <- col_right - 1
            }else{
              flag <- 1
            }
          }
          if (col_right==1) {  # the first column contains non-zero elements
            dummy_right <- dim(z)[2]
          }else{
            dummy_right <- col_right + 1  # leave one column on the right with only zeros
          }

          z.zoomed <- z[dummy_top:dummy_bot, dummy_left:dummy_right]
          x.zoomed <- x[dummy_top:dummy_bot]
          y.zoomed <- y[dummy_left:dummy_right]

          title <- paste("Contour Plot of ", stdnames[i], " (zoomed)",sep="")
          graphics::contour(x.zoomed,y.zoomed,z.zoomed, xlab=x.lab, ylab=y.lab, main=title)

        }else{
          stop('Function argument "show" has to be either "all" or "zoomed"')
        }

      }
    }else{
      graphics::par(mfrow=c(1,1))
      grid <- grid.density.obj[[1]][,1:(numcol-2)]
      x <- grid.density.obj[[1]][,(numcol-1)]
      y <- grid.density.obj[[1]][,(numcol)]
      z <- grid
      title <- paste("Contour Plot of ", stdnames[1], sep="")
      if(show=='all'){
        graphics::contour(x,y,z, xlab=x.lab, ylab=y.lab, main=title)
      } else if (show=='zoomed') {

      # find rows and columns on the edge of the grid density object which consist only of zeros and leave only
      # one such row/column on each side rows on the top
      flag <- 0
      rows_top <- 1
      while(flag !=1){   # find out where non-zero elements start
        if(all(z[rows_top,]==0)){
          rows_top <- (rows_top + 1)
        }else{
          flag <- 1
        }
      }
      if(rows_top==1){  # the first row contains non-zero elements
        dummy_top <- rows_top
      }else{
        dummy_top <- (rows_top - 1)  # leave one row at the top with only zeros
      }

      # rows at the bottom
      flag <- 0
      rows_bot <- dim(z)[1]
      while(flag !=1){   # find out where non-zero elements start
        if(all(z[rows_bot,]==0)){
          rows_bot <- (rows_bot - 1)
        }else{
		  flag <- 1
	    }
      }
      if(rows_bot==dim(z)[1]){  # the last row contains non-zero elements
        dummy_bot <- rows_bot
      }else{
        dummy_bot <- (rows_bot + 1)  # leave one row at the bottom with only zeros
      }

        # columns on the left
        flag <- 0
        col_left <- 1
        while(flag !=1){   # find out where non-zero elements start
          if(all(z[,col_left]==0)){
            col_left <- (col_left + 1)
          }else{
            flag <- 1
		  }
        }
        if(col_left==1){  # the first column contains non-zero elements
          dummy_left <- col_left
        }else{
          dummy_left <- (col_left - 1)  # leave one column on the left with only zeros
        }

        # columns on the right
        flag <- 0
        col_right <- dim(z)[2]
        while (flag !=1) {   # find out where non-zero elements start
          if (all(z[,col_right]==0)) {
            col_right <- (col_right - 1)
          }else{
            flag <- 1
		  }
        }
        if(col_right==1){  # the first column contains non-zero elements
          dummy_right <- dim(z)[2]
        }else{
          dummy_right <- (col_right + 1)  # leave one column on the right with only zeros
        }

        z.zoomed <- z[dummy_top:dummy_bot, dummy_left:dummy_right]
        x.zoomed <- x[dummy_top:dummy_bot]
        y.zoomed <- y[dummy_left:dummy_right]

        title <- paste("Contour Plot of ", stdnames[1], " (zoomed)",sep="")
        graphics::contour(x.zoomed,y.zoomed,z.zoomed, xlab=x.lab, ylab=y.lab, main="Contour Plot of the Pooled Data")

      }else{
        stop('Function argument "show" has to be either "all" or "zoomed"')
      }
	}
  }else{
    stop('Function argument "type" has to be either "combine" or "split"')
  }

}