diff --git a/glucometer_graphs.pl b/glucometer_graphs.pl
index 3c52f61..821eff1 100644
--- a/glucometer_graphs.pl
+++ b/glucometer_graphs.pl
@@ -1,4 +1,10 @@
 #!/usr/bin/perl
+#
+# Perl script to convert CSV output from glucometer into graphs, using gnuplot.
+#
+# Author: Timothy Allen <tim@treehouse.org.za>
+# License: MIT
+#
 
 use strict;
 use warnings;
@@ -10,6 +16,8 @@ my $error = "Usage: $0 --input <CSV file> --output <output PDF> [--max <n.n>] [-
 my @lines;
 my %seen; 
 my @data;
+my @avg_data;
+my $a1c_calc;
 my $gnuplot_data;
 my $total_graphs;
 my $count_graphs = 0; 
@@ -21,12 +29,14 @@ my $output       = "";
 my $max_glucose  = 8;
 my $min_glucose  = 4;
 my $graph_max    = 21;
+my $units        = 'mmol/L';
 my $days_per_page = 2;
 GetOptions ("input=s"  => \$input,          # The name of the CSV file from which to read values
             "output=s" => \$output,         # The name of the PDF file to output
             "high:f"   => \$max_glucose,    # The high end of your target blood glucose level
             "low:f"    => \$min_glucose,    # The low end of your target blood glucose level
             "max:i"    => \$graph_max,      # The highest displayed glucose level on each graph
+            "units:s"  => \$units,          # mmol/L or mg/dL
             "graphs:i" => \$days_per_page)  # The number of days printed on each page
     or die $error;
 
@@ -43,15 +53,9 @@ close( $ifh )
 
 # Set up basic gnuplot options for reading the CSV data
 push @data, qq(
-set datafile separator ","
-set xdata time
-set timefmt "%Y-%m-%d %H:%M:%S"
-#set timefmt "%H:%M:%S"
+set terminal pdf size 29.7cm,21.0cm enhanced font 'Calibri,14' linewidth 1 
+#set output '$output'
 
-set format x "%s" timedate
-set format y "%.2f" numeric 
-
-set samples 10000
 );
 
 # Get the list of days for which to produce graphs
@@ -68,7 +72,7 @@ $total_graphs = scalar keys %seen;
 foreach my $d ( sort keys %seen ) { 
     my $label = "$1$2$3" if ( $d =~ m#(\d{4})-(\d{2})-(\d{2})# );
     push @data, qq(
-\$Data << EOD
+\$Data$label << EOD
 "timestamp","blood glucose","meal","method","comment");
     foreach my $row (@lines) {
         if ( $row =~ s#^"($d )#"$1#ms ) {
@@ -78,13 +82,24 @@ foreach my $d ( sort keys %seen ) {
     push @data, qq(EOD);
 
     push @data, qq(
+set datafile separator ","
+
+set timefmt "%Y-%m-%d %H:%M:%S"
+set format x "%s" timedate
+set format y "%.2f" numeric 
+set samples 10000
+set xdata
+stats \$Data$label using 2
+Mean$label = STATS_mean
+
+set xdata time
 set table \$SmoothData$label
-#plot \$Data using "timestamp":"blood glucose" 
-#plot \$Data using "timestamp":"blood glucose" smooth frequency
-plot \$Data using "timestamp":"blood glucose" smooth mcsplines
-#plot \$Data using "timestamp":"blood glucose" smooth bezier
+#plot \$Data$label using "timestamp":"blood glucose" 
+#plot \$Data$label using "timestamp":"blood glucose" smooth frequency
+plot \$Data$label using "timestamp":"blood glucose" smooth mcsplines
+#plot \$Data$label using "timestamp":"blood glucose" smooth bezier
 unset table
-undefine \$Data
+undefine \$Data$label
 );
 }
 
@@ -96,23 +111,21 @@ push @data, qq(
 reset
 set datafile separator whitespace
 
-set terminal pdf size 29.7cm,21.0cm enhanced font 'Calibri,14' linewidth 1 
-#set output '$output'
 set key off
 set style data lines
 set xdata time
 set timefmt "%H:%M:%S"
+set format x "%H:%M" timedate
+set format y "%.0f" numeric 
+
+set yrange [0:$graph_max]
+# If extended to 23:59, the x grid overlaps with the border
+set xrange ["00:00":"23:58"]
 
 set style line 100 dt 3 lw 1 lc rgb "#202020"
 set style line 101 dt 1 lw 1 lc rgb "#202020"
 set linetype 110 lc rgb "red"
 
-set format x "%H:%M" timedate
-set format y "%.0f" numeric 
-set yrange [0:$graph_max]
-# If extended to 23:59, the x grid overlaps with the border
-set xrange ["00:00":"23:58"]
-
 set lmargin 12
 set rmargin 10
 set tmargin 5
@@ -131,17 +144,34 @@ foreach my $d ( sort keys %seen ) {
 
     $count_graphs++;
 
+    # Algorithms for calculating HbA1c
+    if ( $units =~ /mg/i ) {
+        $a1c_calc = "(AVG + 46.7) / 28.7";
+    } else { # Assume mmol/L
+        $a1c_calc = "(AVG + 2.59) / 1.59";
+    }
+
     push @data, qq(
 set title "Daily Glucose Summary for $title" font "Calibri,18"
 set xlabel "Time" offset 0,-0.25
 set ylabel "Blood glucose" 
 set xtics left tc rgb "#000000"
 set ytics 2    tc rgb "#000000"
-set grid ytics ls 100
+set grid ytics ls 100 front
 
 #set arrow from graph 0,first $min_glucose to graph 1,first $min_glucose ls 6 lw 2 nohead 
 #set arrow from graph 0,first $max_glucose to graph 1,first $max_glucose ls 6 lw 2 nohead
-set object 1 rect from 0,first $min_glucose to graph 1,first $max_glucose fc ls 6 fs solid 0.2 back
+set object 1 rect from graph 0, first $min_glucose to graph 1,first $max_glucose fc ls 6 fs solid 0.2 back
+
+AVG = Mean$label
+AVG_LABEL = gprintf("Average glucose: %.2f", AVG) 
+set object 2 rect at graph 0.9, graph 0.9 fc ls 2 fs transparent solid 0.5 front size char strlen(AVG_LABEL), char 3
+set label 2 AVG_LABEL at graph 0.9, graph 0.9 front center
+
+#A1C = $a1c_calc
+#A1C_LABEL = gprintf("Average A1c: %.1f", A1C) 
+#set object 3 rect at graph 0.07, graph 0.9 fc ls 5 fs transparent solid 0.5 front size char strlen(A1C_LABEL), char 3
+#set label 3 A1C_LABEL at graph 0.07, graph 0.9 front center
 
 #plot \$SmoothData$label using 1:2:( \$2 > $max_glucose || \$2 < $min_glucose ? 110 : $count_graphs ) with linespoints ls 120 lc variable 
 plot \$SmoothData$label using (strftime("%H:%M:%S", \$1)):2:( \$2 > $max_glucose || \$2 < $min_glucose ? 110 : 1 ) with lines lw 3 lc variable 
@@ -157,7 +187,7 @@ set xtics tc rgb "#ffffff00"
 set ytics tc rgb "#ffffff00"
 unset grid
 unset object 1
-set grid xtics ls 101 back
+set grid xtics ls 101
 plot 1/0
 );
 
@@ -168,12 +198,116 @@ plot 1/0
     }
 
 }
+
+# Output data averages by hour of the day
+push @data, qq(
+\$DataAvg << EOD
+"timestamp","blood glucose","meal","method","comment");
+my @sorted_rows;
+foreach my $row (@lines) {
+    if ( $row =~ s#^"\d{4}-\d{2}-\d{2} #"#ms ) {
+        push @sorted_rows, $row;
+    }
+}
+push @data, sort @sorted_rows;
+push @data, qq(EOD);
+
+push @data, qq(
+reset
+set datafile separator ","
+
+set timefmt "%H:%M:%S"
+set format x "%s" timedate
+set format y "%.2f" numeric 
+set samples 10000
+set xdata
+stats \$DataAvg using 2
+MeanTotal = STATS_mean
+
+set xdata time
+set table \$SmoothDataAvg
+plot \$DataAvg using 1:2 smooth bezier
+unset table
+
+set table \$TableDataAvg
+plot \$DataAvg using 1:2 smooth mcsplines
+unset table
+
+undefine \$DataAvg
+
+reset
+set datafile separator whitespace
+
+set key off
+set style data lines
+set xdata time
+set timefmt "%H:%M:%S"
+set format x "%H:%M" timedate
+set format y "%.0f" numeric 
+
+set yrange [0:$graph_max]
+# If extended to 23:59, the x grid overlaps with the border
+set xrange ["00:00":"23:58"]
+
+set style line 100 dt 3 lw 1 lc rgb "#202020"
+set style line 101 dt 1 lw 1 lc rgb "#202020"
+set linetype 110 lc rgb "red"
+
+set lmargin 12
+set rmargin 10
+set tmargin 5
+set bmargin 5
+
+set multiplot title layout $days_per_page,1 
+
+set title "Average Daily Glucose" font "Calibri,18"
+set xlabel "Time" offset 0,-0.25
+set ylabel "Blood glucose" 
+set xtics left tc rgb "#000000"
+set ytics 2    tc rgb "#000000"
+set grid ytics ls 100 front
+
+set object 1 rect from graph 0, first $min_glucose to graph 1,first $max_glucose fc ls 6 fs solid 0.2 back
+
+AVG = MeanTotal
+AVG_LABEL = gprintf("Average glucose: %.2f", AVG) 
+set object 2 rect at graph 0.9, graph 0.9 fc ls 2 fs transparent solid 0.5 front size char strlen(AVG_LABEL), char 3
+set label 2 AVG_LABEL at graph 0.9, graph 0.9 front center
+
+A1C = $a1c_calc
+A1C_LABEL = gprintf("Average A1c: %.1f", A1C) 
+set object 3 rect at graph 0.07, graph 0.9 fc ls 5 fs transparent solid 0.5 front size char strlen(A1C_LABEL), char 3
+set label 3 A1C_LABEL at graph 0.07, graph 0.9 front center
+
+plot \$SmoothDataAvg using ( strftime("%H:%M:%S", \$1) ):2:( \$2 > $max_glucose || \$2 < $min_glucose ? 110 : 1 ) with lines lw 3 lc variable 
+#plot \$TableDataAvg  using (strftime("%H:%M:%S", \$1)):2 with lines lw 1 lc 5, \$SmoothDataAvg using (strftime("%H:%M:%S", \$1)):2:( \$2 > $max_glucose || \$2 < $min_glucose ? 110 : 1 ) with lines lw 3 lc variable 
+
+undefine \$DataAvg
+undefine \$SmoothDataAvg
+undefine \$TableDataAvg
+
+# Add an x grid
+set multiplot previous
+set title "  "
+set xlabel " " offset 0,-0.25
+set ylabel " " 
+set xtics tc rgb "#ffffff00" 
+set ytics tc rgb "#ffffff00"
+unset grid
+unset object 1
+set grid xtics ls 101
+plot 1/0
+
+);
+
 push @data, qq(
 unset multiplot
+#test
 );
 
 # run the data through gnuplot
 $gnuplot_data = join "\n", @data;
+print $gnuplot_data;
 
 open( my $ofh, '>', $output ) 
     or die "Could not open file '$output' $!";
@@ -204,7 +338,8 @@ my $child_exit_status = $? >> 8;
 close( $ofh )
     or warn "close failed: $!";
 
-#open (GNUPLOT, "|gnuplot");
+#open(GNUPLOT, "|gnuplot");
 #print GNUPLOT $gnuplot_data;
+#close(GNUPLOT); 
 
 # vim: set expandtab shiftwidth=4 softtabstop=4 :