Chart showing the terror casualties and incidents per year from 1984 to 2019, considering terror attacks outside insurgent areas (JK, NE, Chhattisgarh). [there is also a graph showing insurgent area attacks]
How it was made:
Data was taken from https://en.wikipedia.org/wiki/List_of_terrorist_incidents_in_India
I converted it into JSON using http://convertjson.com/html-table-to-json.htm (and verified it was converted correctly)
And then made this little Python script to give me the casualties and incidents per year: https://pastebin.com/2NTipuUT
You can verify this data for yourself.
(note that one non-insurgent attack in insurgent area, the 2008 Agartala bombing, was included in the graph; and one insurgent attack on the border of an insurgent area, Pathankot, was not included)
(2019 data upto April 30 considered)