# ==============================================================================
#                             Bar Chart with Grid
#
# Here we'll create a chart of my citations from Google Scholar using a gray 
# background and white horizontal grid lines.
#
#                                                 Kurt Taylor Gaubatz
#                                                 January, 2014
#                                               
# ==============================================================================
# The Data

year = c(1993:2013)                    # Create a vector of years

# The citations data is copied from my Google Scholar page. It looks like it
# is set up to first set the y range for the chart and then the actual 
# citations numbers are a percentage of the max y range, which in this 
# case is 63.
# 

citations1 = c(6.3,11.1,7.9,17.5,38.1,31.7,20.6,34.9,63.5,57.1,61.9,
               61.9,54.0,100.0,84.1,95.2,74.6,84.1,68.3,100.0,60.3)
citations2 = citations1*.63            # Change from % to actual counts

#-------------------------------------------------------------------------------
# We'll plot this in four steps.  
#    1. First we'll create an empty plot with the appropriate x and y ranges.
#    2. Next we'll use the coordinates of the plot area to create a dark
#       gray rectangle the size of the plot area.
#    3. Then we'll create the white grid lines.
#    4. Finally, we'll add the bar chart.
#
# A few idiosyncracies to note:
#
#    > The yaxis="i" option is to prevent R from adding its default overage to
#      the range of the y axis. You'll note that in most R charts the origin
#      starts a little below (0,0). This forces the y axis to start exactly 
#      at 0.
#
#    > When the first plot is set up, the usr parameter identifies the x and y
#      coordinates for the central plot area.  I then use those in the second 
#      step to create the background rectangle in dark gray. We have to do it
#      this way rather than using the bg="gray" parameter setting, because bg=
#      colors in the entire plot window and I just want the internal plot area
#      to be gray.
#
#    > We use the add=T option in the barplot to tell R to add the barplot to
#      an existing plot. We do the barchart last because we want it to be on
#      top of the rectangle and the grid lines.
#
#-------------------------------------------------------------------------------


par(mai=c(1,.75,.25,.25))              # Set margins in inches (B,L,T,R)

# Create an empty plot
plot(x=0, y=0, type="n",               # Plot nothingness
  xlab=NA, ylab=NA,                    # No axis labels
  yaxs="i",                            # No overage on the Y axis
  yaxt="n", xaxt="n",                  # Turn off x and y axes
  xlim=c(1,max(year)-min(year)),       # Set range of x axis
  ylim=c(0,80))                        # Set range of y axis

# Create a medium gray rectange over the plot area
rect(                                  # Use plot area coordinates
    xleft = par()$usr[1],              # Left side x coordinate
    ybottom = par()$usr[3],            # Bottom y coordinate
    xright = par()$usr[2],             # Right side x coordinate
    ytop = par()$usr[4],               # Top y coordinate
    col=gray(.7))                      # Set the color to a medium gray

# Overlay grid lines
grid(nx=NA,                            # No vertical (x) lines
     ny=8,                             # 8 lines for y
     lty=1,                            # Use solid lines
     col="white")                      # Set color to white

# Overlay the barplot
barplot(citations2,                    # Use citation counts for bar heights
        names=year,                    # Use years as names for bars
        width = .65,                   # Set width of bars
        add=T,                         # Add this as an overlay to open plot
        las=2,                         # Rotate bar labels by 90 degrees
        space= .5,                     # Set space between bars
        col="darkslategray")           # Set color of bars to darkish blue gray