Monday, March 30, 2020

CoronaVirus 19 covid19 Disease Modelling with GeoGebra Classic

Modelling with GeoGebra

As a long, faithful and enthusiastic subscriber to the Numberphile channel the above video just arrived.

This post assists you in following the steps to use the online GeoGebra tool to perform the simulation as shown above.

(To make things absolutely clear,  all credit here should go to Ben Sparks and the rest of the Numberphile team)


- Watch the video from start to finish

Impatient people will of course try to work along with simulation first viewing around.   I would recommend patience, watching the whole video first and then

- Download and Install  GeoGebra Classic 6  or
- Start GeoGebra Classic  on Web

- In order to save you will need to register on the website

The basic package is free.

- Watch the video from the start a second time, and follow along entering the formulas that Ben shows us and also creating the on screen slider controls

You have to enter it line by line and here is what he shows. 

S variables for Susceptible
I variables for Infected
R variables for Recovered

Copy and paste each line into the entry area i.e. to the right of the + symbol

S'(t, S, I, R) = - transm * S * I
I' (t, S, I, R) = transm * I - recov * I
R'(t, S, I, R) = recov * I

NSolveODE ( {S',I',R'}, 0, {Sstart,Istart,Rstart}, maxT)

It Didn't Work!!
(Debugging Steps)

- For Marcus, all was going well until I entered the NSolveODE formula.  At that point it refused to acknowledge the formula was correct

- I tried the help but I was convinced all was good.  I note that {} brackets are for a list,  and that function has text inside ()

I tried everything,  eventually Agata deleted the formula and re-entered it (the flippin same!!) and like a good consultant it magically sprung into action.

What a team!

- Once you type in the NSolveODE line and have it accepted it generates three solution lines.   Each line corresponds to a graphed line.

- Then as in the video I renamed each, and also set a colour so that we can see what is going on

- To get the animation you click on the play button for maxT  (which I set as a slider between 0 and 10)

- Change the transmission rate transm, and then press the play button on maxT again to see different graphing results

Still Does Not Work?

I signed up and then saved my work at the following link.  So if you still can't get it working, instead you can directly go to the model that I made and see my version

Link to My Shared

And that completes the lesson for today