When we think about Covid-19, do you wonder the speed of how many people are getting infected? Some will think about exponential functions. Looks like it is spreading exponentially, but it is only for a moment. If the function was like f(t)=2^t (t, day), everyone would definitely get infected, cause the velocity would definitely be 2^t*ln2. The most precise answer would be piecewise function. Right now in China and Korea the rate of change of amount of infectants to time is decreasing.
We would use 10 countries that have Covid-19 infectants.
| Country | 21-03 | 22-03 | dI/dt |
| China | 81,054 | 81,093 | 39 |
| Italy | 53,578 | 59,138 | 5,560 |
| USA | 23,710 | 32,761 | 9,051 |
| Spain | 25,496 | 29,909 | 4,413 |
| Germany | 16,662 | 18,610 | 1,948 |
| Iran | 20,610 | 21,638 | 1,028 |
| France | 14,459 | 16,689 | 2,230 |
| South Korea | 8,897 | 8,961 | 64 |
| Switzerland | 6,747 | 7,014 | 267 |
| UK | 5,018 | 5,683 | 665 |
Average: 2,418.5people/day
| Country | dI/dt Maximum |
| China | 15,152 |
| Italy | 6,557 |
| USA | 9,339 |
| Spain | 4,946 |
| Germany | 4,062 |
| Iran | 1,411 |
| France | 1,861 |
| South Korea | 1,062 |
| Switzerland | 1,378 |
| UK | 1,035 |
Average: 4,675.3people/day
According to the graph, 2,419 people get infected per day. As more people get infected, more cases will be reported. Graphically, it is similar to exponential function, and then it becomes similar to logarithm function. We all have to be careful from COVID-19.
