<% local data, viewlibrary, page_info, session = ... %> <% if (data.graph.width) then %>

<% else %>

No valid output available!

Please check if your syntax is right.
Read http://oss.oetiker.ch/rrdtool/doc/rrdgraph.en.html for help.

<% io.write(tostring(data.value)) %>

<% end %>