fancyaxis.R

##     fancyaxis: Draw axis which shows minimum, maximum, quartiles
##                 and mean
##
##     Copyright (C) 2005 Steven J. Murdoch <http://www.cl.cam.ac.uk/users/sjm217/>
##
##     This program is free software; you can redistribute it and/or modify
##     it under the terms of the GNU General Public License as published by
##     the Free Software Foundation; either version 2 of the License, or
##     (at your option) any later version.
##
##     This program is distributed in the hope that it will be useful,
##     but WITHOUT ANY WARRANTY; without even the implied warranty of
##     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
##     GNU General Public License for more details.
##
##     You should have received a copy of the GNU General Public License
##     along with this program; if not, write to the Free Software
##     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

##     This is very much a work in progress and still of alpha
##     quality. See the example file for usage. It currently does not
##     deal with logarithmic scales properly and needs manual tweaking
##     of several values to suit different data and output device
##     resolution. Comments and suggestions are appreciated. My
##     contact details can be found here:
##       http://www.cl.cam.ac.uk/users/sjm217/#contact
##
##     The design of the graph is based on a scatterplot presented in
##     "The Visual Display of Quantitative Information", Edward Tufte.
##     Thanks to Paul Murrell for assistance with handling the log axes
##
##     $Id$

# Add a small amount of noise to a numeric vector, preserving minimum
# and minimum
clippedjitter <- function(x, ...) {
  # x:   numeric to which jitter should be added.
  # ...: parameters passed to jitter()
  
  mi <- min(x)
  ma <- max(x)

  len=length(x)

  # Find a position for the min and max
  mipos <- ((1:len)[x==mi])[1]
  mapos <- ((1:len)[x==ma])[1]
  
  # The standard jittered data
  xj <- jitter(x, ...)

  # Find the elements which are outside the limits
  under <- xj<mi
  over <- xj>ma

  # Find the distance away from the limit
  dunder <- mi-xj[under]
  dover <- xj[over]-ma

  # Reflect over the limit
  repunder <- dunder+mi
  repover <- ma-dover

  # Replace out of limit values with the reflected ones
  xj[under] <- repunder
  xj[over] <- repover
  
  # Replace a jittered min/max with the original min/max
  xj[mipos] <- mi
  xj[mapos] <- ma
  
  # Return updated array
  xj
}

# Draw a rug plot, but ommit the baseline (actually, draw over it
minimalrug <- function(x, lwd=0.7, tcl=0.3, ...) {
  # x:   a numeric vector
  # ...: parameters passed to rug()
  
  # Rounded ends don't work well with erasing one end
  oldlend <- par(lend = "butt")
  on.exit(par(oldlend))

  # Used for overwriting the axis line to leave tickmarks
  bg <- par("bg")
  if (bg == "transparent")
    bg <- "white"

  # Draw the rug
  rug(x, ticksize=NA, lwd=lwd, ...)
  # Acrobat shows "shadows" around a line erased with a line
  #  of similar width, so use a thicker line
  overlwd=1
  # Remove the baseline (... is put first to allow other the other
  #  parameters to override it)
  axis(..., at=x, col=bg, tcl=0, label=FALSE, lwd=overlwd)
}
  
fancyaxis <- function(side, summ, at=NULL, mingap=0.5, digits=2,
                      shiftfac=0.003, gapfac=0.003) {
  # side: like axis()
  # summ: a summary object, for example returned by summary()
  # mingap: the smallest gap permitted between two tickmarks,
  #         expressed as a fraction of the default tickmark gap
  # digits: the number of digits to round minimum and maximum to
  # shiftfac: proportion of plot width used to offset the broken axis
  # gapfac: proportion of plot width used to leave for median gap
  
  # TODO:
  # Deal with case where length(axTicks)<2
  # Deal with logarithmic axis case properly, as axTicks difference
  #  is not uniform.
  
  # Get summary information
  amin <- summ[1]
  aq1 <- summ[2]
  amed <- summ[3]
  amean <- summ[4]
  aq3 <- summ[5]
  amax <- summ[6]

  # Find out the properties of the side we are doing
  parside <-
    if (side==1){
      # Does the outside of the plot have larger or smaller vales
      flip <- 1
      # Are we on the xaxis
      xaxis <- TRUE
      # Is this axis logarithmic
      islog <- par("xlog")
      # Is the other axis logarithmic
      otherlog <- par("ylog")
      # Relevant index of par("usr")
      3
    }
    else if (side==2) {
      flip <- 1
      xaxis <- FALSE
      islog <- par("ylog")
      otherlog <- par("xlog")
      1
    }
    else if (side==3) {
      flip <- -1
      xaxis <- TRUE
      islog <- par("xlog")
      otherlog <- par("ylog")
      4
    }
    else if (side==4) {
      flip <- -1
      xaxis <- FALSE
      islog <- par("ylog")
      otherlog <- par("xlog")
      2
    }

  # Calculate default positions of ticks
  if (is.null(at))
    ticks <- axTicks(side)
  else
    ticks <- at

  # Remove any ticks outside the range
  ticks <- ticks[(ticks>=amin) & (ticks<=amax)]
  
  # Calculate the minimum desired gap between ticks
  numticks <- length(ticks)
  if (islog)
    axgap <- (log10(ticks[numticks])-log10(ticks[numticks-1]))*mingap
  else
    axgap <- (ticks[numticks]-ticks[numticks-1])*mingap

  # Get new range of tickmarks
  numticks <- length(ticks)
  firsttick <- ticks[1]
  lasttick <- ticks[numticks]
  
  # If max tick will be too close to the last tick, replace it,
  #  otherwise append it
  if (islog && (log10(amax) - log10(lasttick) < axgap)) {
    ticks[numticks]<-amax
  } else if (amax - lasttick < axgap) {
    ticks[numticks]<-amax	
  } else {	
    ticks<-c(ticks,amax)
  }
  
  # Similarly for first tick
  if (islog && (abs(log10(amin)-log10(firsttick)) < axgap)) {
    ticks[1]<-amin	
  } else if (firsttick - amin < axgap) {
    ticks[1]<-amin	
  } else {	
    ticks<-c(amin, ticks)
  }

  # Format the labels. min and max should have as many
  #  trailing zeros they were rounded to, the others
  #  should have the minimum needed to represent the tick marks
  numticks <- length(ticks)

  # Min and max
  lmin <- format(round(ticks[1], digits), nsmall=digits, trim=TRUE)
  lmax <- format(round(ticks[numticks], digits), nsmall=digits, trim=TRUE)

  # The others
  middle <- format(ticks[2:(numticks-1)], trim=TRUE)

  # Combine them
  labels <- c(lmin,middle,lmax)

  # Draw the axis
  oldlend <- par(lend = "butt")
  on.exit(par(oldlend))

  # Used for overwriting the axis line to leave tickmarks
  bg <- par("bg")
  if (bg == "transparent")
    bg <- "white"

  lwd=0.7
  # Draw the axis and tickmarks
  axis(side, ticks, labels=FALSE, col="gray50", lwd=lwd)
  # Erase the axis
  overlwd=1
  axis(side, ticks, labels=FALSE, col=bg, tcl = 0, lwd=overlwd)
  # Draw the labels
  axis(side, ticks, labels=labels, tick=FALSE)

  # Axis position
  base<-par("usr")[parside]

  # Width and height in user units
  plotwidth <- diff(par("usr")[1:2])
  plotheight <- diff(par("usr")[3:4])

  # Shift for the q2 and q3 axis from the base (in inches)
  shift <- par("pin")[1]*shiftfac*flip
  # Gap for the median
  gap <- par("pin")[1]*gapfac
  
  # Shift for the mean pointer away from the axis
  meanshift <- par("cin")[1]*0.5*flip

  # Scale lengths so both axes are equal on output device
  if (!xaxis) {
    # Y axis

    # Convert inches into user units
    shift <- shift/par("pin")[1]*plotwidth
    meanshift <- meanshift/par("pin")[1]*plotwidth
    gap <- gap/par("pin")[2]*plotheight
  } else {
    # X axis

    # Convert inches into user units
    shift <- shift/par("pin")[2]*plotheight
    meanshift <- meanshift/par("pin")[2]*plotheight
    gap <- gap/par("pin")[1]*plotwidth
  }

  if (islog) {
    # Log case on this axis (affects gap)
    lmed <- log10(amed)
    gapt <- 10^(lmed + gap)
    gapb <- 10^(lmed - gap)
  } else {
    # Linear case on this axis
    gapt <- amed + gap
    gapb <- amed - gap
  }

  # Position of q2 and q3 axis segments
  offset <- base + shift

  # Which segment is the mean in?
  if((amean>aq3) || (amean<aq1)) {
    # Mean is in q1/q4, so move relative to base
    meanbase <- base - meanshift
  } else {
    # Mean is in q2/q3, so move relative to shifted base
    meanbase <- offset - meanshift
  }

  if (otherlog) {
    # Log case on the other axis (affects shift, base, meanshift)
    meanbase <- 10^meanbase
    offset <- 10^offset
    base <- 10^base
  }

  # Stops the lines overrunning
  par(lend = "butt")

  # Line width for axis lines
  lwd=1

  # Draw q1 and q4 axis segments
  if (!xaxis) {
    #     xs,         ys,          Don't clip, Line width, Don't overlap 
    lines(rep(base,2),c(amin,aq1), xpd=TRUE, lwd=lwd)
    lines(rep(base,2),c(aq3,amax), xpd=TRUE, lwd=lwd)
  } else {
    lines(c(amin,aq1),rep(base,2), xpd=TRUE, lwd=lwd)
    lines(c(aq3,amax),rep(base,2), xpd=TRUE, lwd=lwd)
  }

  # Draw q2 and q3 axis segments
  if (!xaxis) {
    lines(rep(offset,2),c(aq1,gapb), xpd=TRUE, lwd=lwd)
    lines(rep(offset,2),c(gapt,aq3), xpd=TRUE, lwd=lwd)
  } else {
    lines(c(aq1,gapb),rep(offset,2), xpd=TRUE, lwd=lwd)
    lines(c(gapt,aq3),rep(offset,2), xpd=TRUE, lwd=lwd)
  }
  

  # Draw the mean
  if (!xaxis) {
    points(meanbase, amean, pch=18, cex=0.7, col="red", xpd=TRUE)
  } else {
    points(amean, meanbase, pch=18, cex=0.7, col="red", xpd=TRUE)
  }
}

# Draw a stripchart on an axis, showing marginal frequency
# TODO: Does not handle log axes well
axisstripchart <- function(x, side, sshift=0.3) {
  # x:    the data from which the plots are to be produced.
  # side: as in axis()
  
  # Find out the properties of the side we are doing
  parside <-
    if (side==1){
      # Does the outside of the plot have larger or smaller vales
      flip <- 1
      # Are we on the yaxis
      yaxis <- FALSE
      # Relevant index of par("usr")
      3
    }
    else if (side==2) {
      flip <- 1
      yaxis <- TRUE
      1
    }
    else if (side==3) {
      flip <- -1
      yaxis <- FALSE
      4
    }
    else if (side==4) {
      flip <- -1
      yaxis <- TRUE
      2
    }

  # Axis position
  base<-par("usr")[parside]
  
  # Width and height in user units
  plotwidth <- diff(par("usr")[1:2])
  plotheight <- diff(par("usr")[3:4])
  
  # Shift for the q2 and q3 axis from the base (in inches)
  shift <- par("pin")[1]*0.003*flip
  # Gap for the median
  gap <- par("pin")[1]*0.003
  # Shift for the mean pointer away from the axis
  meanshift <- par("cin")[1]*0.5*flip
  # Shift away from the q2 and q3 axis for the stripchart
  stripshift <- par("cin")[1]*sshift*flip
  
  # Scale lengths so both axes are equal on output device
  if (yaxis) {
    shift <- shift/par("pin")[1]*plotwidth
    meanshift <- meanshift/par("pin")[1]*plotwidth
    stripshift <- stripshift/par("pin")[1]*plotwidth
    gap <- gap/par("pin")[2]*plotheight
  } else {
    shift <- shift/par("pin")[2]*plotheight
    meanshift <- meanshift/par("pin")[2]*plotheight
    stripshift <- stripshift/par("pin")[2]*plotheight
    gap <- gap/par("pin")[1]*plotwidth
  }

  # If vertical, stripchart assumes offset is a factor of character
  # width, if horizontal, character height (bug?). So correct for this
  if (yaxis)
    offset=flip*par("cin")[2]/par("cin")[1]
  else
    offset=flip

  # Don't clip the chart
  oldxpd <- par(xpd = TRUE)
  on.exit(par(oldxpd))
  
  stripchart(x, method="stack", vertical=yaxis, offset=offset, pch=15,
             cex=0.2, add=TRUE, at=base+shift+stripshift, col="red")
}