I don’t believe that WordPress has any line graph capabilities of its own. But php does, so you could code your own.
There is an example on this page:
http://php.net/manual/en/ref.image.php
I found it using this Google query:
site:php.net "line graph"
so you can try that if the example doesn’t do the job for you.
I’m not sure how that works. Are there more remedial instructions on how to do this somewhere? I should note that I am not the owner of the blog.
Creating your own php code and getting WordPress to execute it and display the results where you want them on your WordPress site goes under the heading of Advanced Techniques in most circumstances. If you want to add php code to a WordPress Page or Post, you must first install a Plug-in. Or make your own changes to (php code in) the Template file that generates a Page or Post. A plug-in is a modification to WordPress that is not written by the WordPress development team; plug-ins are described here: http://codex.ww.wp.xz.cn/Plugins Templates are described here: http://codex.ww.wp.xz.cn/Using_Themes
You can also directly add php code to a Template. And can even have a custom Template file just for one Page as described in the Page Templates section of http://codex.ww.wp.xz.cn/Pages#Page_Templates
http://ww.wp.xz.cn/extend/plugins/simple-graph/
is a plugin that does simple line graphs….Just a note, it is quite out of date….I haven’t seen a newer one. I know it works on my wife’s blog….
Not sure if this will fit the bill but the plugin easy chart builder does line graphs
