Your canonical URL should probably (I'll explain why so tentative) go to the chart tool in its starter state; that is,
example.com/chart. Think about it this way. You want search engines to index only one ultimate version of this page; that's the one that will rank in search results. Your visitors will land on this page and share this URL.
Your tool probably has many configurations that are specific to what each individual user wants. You probably don't want someone to land on a page where the tool already comes with someone's preferred configurations and then have to undo those filters and change them to what they actually need.
There are cases, though, where you want to leave some filters in. For example, in an e-commerce store, you might have shoes that come in three colors, and you want the black ones to be the default. Or maybe in your tool, you have a default time range - let's say a week - that you want the visitors to land on.
So it depends on your business case. If there is a "blank slate" state for your tool, that's the one you want to be canonical. If there is no blank slate and a default time range or other default identifier has to be present, that's the one you use. Just make sure it's only one that you canonicalize.