Just like your previous chart on what you arbitrarily define "Ideologically motivated incidents of murder", this chart is also extremely misleading and inaccurate.
Go to the ADL heatmap website, look for the "Incident type" box and click on the icon (i) next to it. The ADL site should display the "Definitions of Incident Types:", e.g.: for "Extremist Murders", the following definition should be displayed: "Extremist Murders: Killings connected to members of extremist groups and adherents of extremist ideologies. Includes both ideological and non-ideological killings..."
You seem to totally ignore both what their data says and their own definitions. This is why your original research is being massively contradicted by both the data from United States Government Accountability Office (GAO) and the the fact-checkers at PolitiFact. According to them, the total number of domestic terrorist attacks (from September 12, 2001 through December 31, 2016) for Right-wing extremists is 62; for Islamist-extremists is 23. Your chart has more than 200 incidents for approx half that time-span (you cover 2008->2017, GAO & PolitiFact cover 2001-09-12-2016->12-31). ADL has similar numbers with GAO and PolitiFact if you only include ideologically motivated incidents and not all incidents like you currently do (e.g.: a man killing another because he made inappropriate comments about his daughter or girlfriend, or because of a failed drug-deal, is not an ideologically motivated murder no matter how much you want it to be).
Here are a few examples which are NOT labeled by ADL as terrorism but are labeled as murder: which you nevertheless include in your charts (the examples are only for the year=2013, but there's much more for all the years covered by your chart):
1.1) "8/13/2013 Tulsa, OK - Ronnie Dean Haskins III murdered a man who reportedly patted Haskins's daughter on her behind and made inappropriate comments";
1.2) "12/30/2013 San Diego, CA - San Diego Skins member Joseph Anthony Hill murdered one person and injured another in a feud over disrespecting Hill's girlfriend and a drug debt"; etc
1.3) "10/25/2013 Ingot, CA - White supremacist Joshua McCormick killed two people during a robbery";
1.4) "8/14/2013 Waltham, MA - White supremacist Jared Remy, who had an "88" tattoo on his neck, murdered his girlfriend";
