Most graphs mapping the spread of the coronavirus measure against time giving an exponential curve upwards.
By removing the time element the growth becomes a straight line. It is then easy to see when the spread drops away from the growth line, as in China, and where the spread is rocketing off into the unknown as can be seen in Aatish Bhatia’s graphs.
So we stay at home avoiding contact with other people to stop the virus from spreading and break away from that line of growth as quickly as possible.
Update: And this…