Basically, I want the user to be able to change the type of the graph by clicking a drop down menu: BarRenderer, PieRenderer, etc. The data is the same. I know I can call $.jqpl
I think the docs are ok, but you will find hidden features inside of it or quirks that aren't documented. IIRC (it's been a while) you will have to call $.jqplot() again but you first need to .empty() your target or you'll get extra / messed up canvases.
What you really need to do is save your data and allow it to be called later:
//This isn't real jqplot syntax but it should give you a good idea of what I'm explaining
var charts = [{name:"chart1",renderer:"pie",data:[[1,2],[2,3]]}]
$('#graph').jqplot(charts[0]);
//later
charts[0].renderer = "bar";
$('#graph').empty().jqplot(charts[0]);