From the data tool (data.cpdp.co), you can filter all the complaints data and the graphs by year if you type a year (for example "2010") into the search bar and select the incident year filter from the list of filter options that appear. 

If you want to combine data from multiple years, then you can pin multiple filters together by clicking the "pin" symbol in each filter after you add it.

If you want to look at the investigations that were closed in a particular year (rather than the complaint incidents that happened in a particular year), then you'll need to use the raw data available here.