Iframe 'Visits over time graph' not persisting options

I’m using iframes to display my graphs on a third party dashboard but I am having some trouble with the ‘Visits over time graph’. I would like to display multiple lines in the iframe such as ‘visitors’ and ‘unique visitors’ but on refresh it defaults to just the ‘visitors’ line. Is there any way to persist this data in the url or something similar? I’ve been looking through the documentation but can’t seem to find anything.