# ------- Graph the values in the form of associative array 


$sql = "SELECT MAX(`discri`) AS mmax, MIN(`discri`) AS mmin FROM question_stats WHERE quiz_id = '$qid'";


$res = $db->sql_query($sql);


if (!$res) {


      echo("<p>Error performing query: " . mysql_error() . "</p>");


      }


$row = $db->sql_fetchrow($res);


$min = $row['mmin']; 


$max = $row['mmax'];


$ranges = get_ranges($min, $max);





$chart = $db->sql_query("SELECT `discri`, COUNT(`discri`) AS occurrence FROM question_stats WHERE quiz_id = '$qid' GROUP BY `discri` ORDER BY `discri`");    


while( $row = $db->sql_fetchrow($chart)) {    


    $base = get_base($row['discri']);        


    $values[$base] += $row['occurrence'];   


} 





 //Setting the chart label variables


$graphTitle = "Discriminator"; 


$xLabel    = "Range "; 


$yLabel    = "Questions"; 





# ----getting the size of the fonts


$Titlefontwidth  = imagefontwidth(2);


$Titlefontheight = imagefontheight(2);


$fontwidth  = imagefontwidth(2);


$fontheight = imagefontheight(2);





# ----getting the color of the fonts


$blue = imagecolorallocate($img, 3,12,94); 





#-----setting the image dimensions 


   $img_width=800;


   $img_height=600; 


   $margins=40;





 


   # ---- Find the size of graph by substracting the size of borders


   $graph_width=$img_width - $margins * 2;


   $graph_height=$img_height - $margins * 2; 


   $img=imagecreate($img_width,$img_height);





 


   $bar_width=30;


   $total_bars=count($values);


   $gap= ($graph_width- $total_bars * $bar_width ) / ($total_bars +1);





 


   # -------  Define Colors ----------------


   $bar_color=imagecolorallocate($img,0,64,128);


   $background_color=imagecolorallocate($img,240,240,255);


   $border_color=imagecolorallocate($img,200,200,200);


   $line_color=imagecolorallocate($img,220,220,220);


 


   # ------ Create the border around the graph ------





   imagefilledrectangle($img,1,1,$img_width-2,$img_height-2,$border_color);


   imagefilledrectangle($img,$margins,$margins,$img_width-1-$margins,$img_height-1-$margins,$background_color);





 


   # ------- Max value is required to adjust the scale   -------


   $max_value=max($values);


   $ratio= $graph_height/$max_value;





 


   # -------- Create scale and draw horizontal lines  --------


   $horizontal_lines=20;


   $horizontal_gap=$graph_height/$horizontal_lines;





   for($i=1;$i<=$horizontal_lines;$i++){


      $y=$img_height - $margins - $horizontal_gap * $i ;


      imageline($img,$margins,$y,$img_width-$margins,$y,$line_color);


      $v=intval($horizontal_gap * $i /$ratio);


      imagestring($img,0,5,$y-5,$v,$bar_color);





   }


   


#----Graph Title------------


imagestring($img, 4, 400, 20, $graphTitle, $blue); 


 


#----X-Axis----------------


imagestring($img, 4, 400, 580, $xLabel, $blue); 


 


#----Y-Axis----------------


imagestringup($img, 4, 20, 300, $yLabel, $blue); 


 


 


 


   # ----------- Draw the bars here ------


   for($i=0;$i< $total_bars; $i++){ 


      # ------ Extract key and value pair from the current pointer position


      list($key,$value)=each($values); 


      $x1= $margins + $gap + $i * ($gap+$bar_width) ;


      $x2= $x1 + $bar_width; 


      $y1=$margins +$graph_height- intval($value * $ratio) ;


      $y2=$img_height-$margins;


      imagestring($img,0,$x1+3,$y1-10,$value,$bar_color);


      imagestring($img,0,$x1+3,$img_height-15,$key,$bar_color);      


      imagefilledrectangle($img,$x1,$y1,$x2,$y2,$bar_color);


   }


   header("Content-type:image/png");


   imagepng($img);