The Multigraph WordPress plugin makes it easy to create graphs on pages in a WordPress site.
To install the plugin, download the plugin zip file from the Multigraph download page, and unzip it into the "wp-content/plugins" directory in your copy of WordPress. Then login to WordPress as an administrator and enable the plugin. Also, add "text/xml" and "text/csv" to WordPress's list of allowed file types, in the "Mime Types" section under WordPress's "Settings" menu.
Once the plugin is enabled and WordPress is configured to allow text/xml and text/csv mime types, follow these steps to add a graph to any post:
To make a change to a MUGL file that you have uploaded, delete the original MUGL file from the media library, then upload the new file, giving it the same name (and title) as the old one.