I tried this with your events in a notepad as follows:
Sep 15 2017 07:06:07 app=yahoo dataconsumed=50
Sep 15 2017 08:16:07 app=skype dataconsumed=150
Sep 14 2017 10:26:07 app=facebook dataconsumed=10
Sep 14 2017 12:26:07 app=facebook dataconsumed=5
Sep 13 2017 7:26:07 app=yahoo dataconsumed=10
Sep 13 2017 9:26:07 app=skype dataconsumed=50
Sep 12 2017 3:26:07 app=facebook dataconsumed=80
Sep 12 2017 1:26:07 app=facebook dataconsumed=0
| eval t=strftime(_time,"%Y-%m-%d")
| eval t1=strptime(t,"%Y-%m-%d")
| eval d=strftime(relative_time(now(),"-2d"),"%Y-%m-%d")
| eventstats max(t1) as f by app
| eval d1=t1-f
| eval c=if(f=t1,"c",if(d1=d,"p","nc"))
| chart sum(dataconsumed) by app,c
| eval dataconsumed=c-nc
|eval gainer_or_looser=if(dataconsumed >0,"gainer",if(dataconsumed=0,"even","looser"))
| fields app,gainer_or_looser,dataconsumed
| sort - app
... View more