Falla en creacion de graficas (JpGraph)

[hoberwilly]

Estimados amigos, que estara pasando con el siguiente error que me lanza:
Fatal error: Cannot instantiate non-existent class: graph in /data/members/free/tripod/es/h/o/b/hoberwilly/htdocs/estadistica.php on line 9
cuando uso este codigo recogido de la web:

Código php:

<!-- <?php 
include ("jpgraph/jpgraph.php"); 
include ("jpgraph/jpgraph_line.php"); 
 
// Some data 
$ydata = array(11.5,3,8,12,5,1,9,13,5,7); 
 
// Create the graph. These two calls are always required 
$graph = new Graph(450,250,"auto"); 
$graph->SetScale("textlin"); 
$graph->img->SetAntiAliasing(); 
$graph->xgrid->Show(); 
 
// Create the linear plot 
$lineplot=new LinePlot($ydata); 
$lineplot->SetColor("black"); 
$lineplot->SetWeight(2); 
$lineplot->SetLegend("Horas"); 
 
// Setup margin and titles 
$graph->img->SetMargin(40,20,20,40); 
$graph->title->Set("Ejemplo: Horas de Trabajo"); 
$graph->xaxis->title->Set("Días"); 
$graph->yaxis->title->Set("Horas de Trabajo"); 
$graph->ygrid->SetFill(true,'#[email protected]','#[email protected]'); 
//$graph->SetShadow(); 
 
// Add the plot to the graph 
$graph->Add($lineplot); 
 
// Display the graph 
$graph->Stroke(); 
?> 
-->
 

Y gracias por la ayuda brindada