http://www.aditus.nu/jpgraph/index.php

# wget http://hem.bredband.net/jpgraph2/jpgraph-3.0.7.tar.bz2
# tar jxvf jpgraph-3.0.7.tar.bz2
# mkdir /usr/local/share/php
# mv docportal /usr/local/share/php

# mkdir /var/www/html/mantisbt/jpgraph
# mv src/* mantisbt/jpgraph/
			

php.ini

# vim /etc/php.ini
include_path = ".:/usr/share/pear/:/var/www/html/mantisbt/jpgraph/"
			

config_inc.php

# vim config_inc.php
$g_use_jpgraph = ON;
$g_jpgraph_path = '/var/www/html/mantisbt/jpgraph/';
			

Don't forget to add the trailing '/'.