I am unfamiliar with EasyUI, and doubt if anybody else here is. You should seek support from EasyUI. All we can do is make some guesses.
When you say your code doesn't "work", what exactly do you mean? Did you examine the DOM using the built-in debug tools in your desktop browser, and see that the data- attributes did not change? Or did you simply observe that your change had no visual effect?
There is nothing wrong with the code you show. It should change the data-attributes. We can guess that perhaps there is some error in code prior to this, causing your code not to run at all. Did you check for errors on the javascript console?
But we can't guess if EasyUI pays attention to changes made after widgets are initialized! You need to ask the authors of EasyUI.
(Edit: won't work...)
However, changing data-attributes they way you show is not the usual way. Most plugins would use the jQuery .data() function to access jQuery's internal cache of the values. Assuming this is so, there is a much easier way:
$('#east').data('options').collapsed = true;
This way, you don't need to concern yourself with setting all of the other attributes. You can easily change just one.
Note that since this doesn't change the actual attribute, you cannot use the browser's inspection/debugging tool to verify, as you can when you change the attribute.
Again, we cannot guess if EasyUI will pay attention to changes made after widget initialization. Perhaps there is some "refresh" function that needs to be called, perhaps they provide a function to collapse/expand, perhaps it is just not supported. We can't guess.
That product comes with support for a year. If your support expired, I'd suggest you renew it!