I just did this for a quick fix:
1) Created a user named "Urchin" group "psaserv" with nologin.
2) Put the following in a vhost.conf for the domain I wanted stats for:
CODE
LogFormat "%h %v %u %t "%r" %>s %b "%{Referer}i" "%{User-Agent}i" "%{Cookie}i"" special
CustomLog /home/httpd/vhosts/domain.com/statistics/logs/special_log special
3) Create a custom logfile:
CODE
touch /home/httpd/vhosts/domain.com/statistics/logs/special_log
4) Tell Plesk the vhost.conf is there:
CODE
/usr/local/psa/admin/sbin/websrvmng --reconfigure-all
5) CHMOD the statistics dir:
CODE
chmod 755 /home/httpd/vhosts/domain.com/statistics
6) Go play with Urchin!
I'm still playin around trying to get it setup so that I don't have to chmod the statistics dir to 755 instead of the default 550. 755 scares me.