Dear All,

I am in the midst of doing up my thesis paper and have encountered some problem with regards to D-I-D Model with multiple treatment groups. Couldn't find anything online so I was hoping that fellow users here could help me out!

Basically I am trying to find out the effects of school closure on property prices. I have 3 different groups here.
Group 1 (treatment group) - Property 0km to 1km
Group 2 (treatment group) - Property 1km to 2km
Group 3 (control group) - Property 2km to 4km

May I know how I could incorporate them into one single equation? Thank you in advance for all your help!