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And I am having serious misgivings about posting it, nonetheless, many people have expressed deep concerned, and I'm doing the same, only with actual data. I m

And I am having serious misgivings about posting it, nonetheless, many people have expressed deep concerned, and I'm doing the same, only with actual data. I made it clear the limits of my knowledge - which may still not excuse me, however I have to ask if you are an epidemiologist and if so, please tell me how to model the data better. And I don't mean randomly google up some papers to dump here and pretend you are an expert (unless you are). How far can I extrapolate e^x before it becomes useless? What are the confidence limits I can use in the extrapolation? How much can I approximate the logistic function with an exponential, when as now, the cases are currently a small fraction of the population? Why is this site http://nrg.cs.ucl.ac.uk/mjh/covid19/ http://nrg.cs.ucl.ac.uk/mjh/covid19/ done by experts using log axis any different from mine using curve fitting with exponentials? Why does http://nrg.cs.ucl.ac.uk/mjh/covid19/#w http://nrg.cs.ucl.ac.uk/mjh/covid19/#w say the USA is 11.5 days behind Italy whereas my amateur attemp suggest ~9 days? (and yes, I wish I'd seen these graphs before I posted) What else have I missed? Criticise freely, with reason, don't just accuse me of misinformation because I posted my fears, which others have done too, only I did the maths. Now please excuse me while I look at the logistics curve and compare its early stages with exponentiation.

YeGoblynQueenne 7y ago
>> And I am having serious misgivings about posting it, nonetheless, many people have expressed deep concerned, and I'm doing the same, only with actual data. There is no "actual data" in your comment above. There is a claim that you make that you have graphed some data, but no graphs and no data. Also, it doesn't take an epidemiologist to know that a non-epidemiologist should not play at epidemiology. The other poster doesn't have any responsibility to tell you "how to model the data better".
- throwaway_pdp09 7y ago
  > There is no "actual data" in your comment above There is in http://nrg.cs.ucl.ac.uk/mjh/covid19/#w http://nrg.cs.ucl.ac.uk/mjh/covid19/#w which I said matches what I've found rather well. > The other poster doesn't have any responsibility to tell you "how to model the data better". Yes he does,
  - NateEag 7y ago
    > There is in http://nrg.cs.ucl.ac.uk/mjh/covid19/#w http://nrg.cs.ucl.ac.uk/mjh/covid19/#w which I said matches what I've found rather well There may be data there, but if I understand you correctly you did not have it when you made your first post. It is therefore inadmissible evidence as to whether your first post was a reasonable thing to write. > Yes he does, If you have decided you want to be an epidemiologist, or at least to learn their skillset, whose responsibility is it to fulfill that desire? I don't think there is a reasonable answer to that other than "mine."
    - throwaway_pdp09 7y ago
      > but if I understand you correctly you did not have it when you made your first post correct > It is therefore inadmissible evidence as to whether your first post was a reasonable thing to write. Completely wrong. I approximated the lowest part of a logistic function with e^x, which is reasonable for small values. Given it matched well with professional epidemiologists' graphs, it suggests I'm getting it approximately right. > whose responsibility is it to fulfill that desire? Mine and yours. Don't stick 'reasonable' on your replies and suppose it insures you in any way cos it doesn't.
      - andrepd 7y ago
        Mate I can start to pontificate randomly about aeronautics design, and you can very well tell me to shut up with no requirement that you are an expert yourself.
      - alien_ 7y ago
        There's a quote that states that all models are wrong, some happen to be useful. With this in mind I think we should stop nitpicking on non-specialists who try to raise awareness of this pandemic. Yes there might be some differences from what a specialist would have done. Due to the speed at which the situation evolves and the inability to test everyone daily there are lots of unknowns so even a specialist may not be able to give a more much precise figure, everything is going to be a rough estimate. This is a very serious situation and it's better to err on the caution side, people's lives depend on everyone doing their part. Non-constructive criticism of people who raise awareness will erode people's buy-in and people will die because of this.
marvin 7y ago
The "behind Italy" number must refer to the number of days after Italy the area reached 100 confirmed cases. Because those numbers obviously don't reflect an extrapolation of the exponential function even 10 days into the future, even corrected for a reduction in the coefficient when numbers grow above 10.000.
hanche 7y ago
You are absolutely right that the early phase of logistic growth is practically indistinguishable from exponential growth. As to what extent this observation is useful when applied to the current situation, I don't know – I am a mathematician, not an epidemiologist. But as a rough guide to aid understanding, I think it probably has some merit.
- throwaway_pdp09 7y ago
  Thanks, it's nice to have an expert around! I was going to plot the divergence between the two but got seriously despondent and hit the bottle. Trying to sober up now. May I ask, what area do you work in, numerical, discrete, logic, other?

YeGoblynQueenne 7y ago

>> And I am having serious misgivings about posting it, nonetheless, many people have expressed deep concerned, and I'm doing the same, only with actual data. There is no "actual data" in your comment above. There is a claim that you make that you have graphed some data, but no graphs and no data. Also, it doesn't take an epidemiologist to know that a non-epidemiologist should not play at epidemiology. The other poster doesn't have any responsibility to tell you "how to model the data better".

throwaway_pdp09 7y ago
> There is no "actual data" in your comment above There is in http://nrg.cs.ucl.ac.uk/mjh/covid19/#w http://nrg.cs.ucl.ac.uk/mjh/covid19/#w which I said matches what I've found rather well. > The other poster doesn't have any responsibility to tell you "how to model the data better". Yes he does,
- NateEag 7y ago
  > There is in http://nrg.cs.ucl.ac.uk/mjh/covid19/#w http://nrg.cs.ucl.ac.uk/mjh/covid19/#w which I said matches what I've found rather well There may be data there, but if I understand you correctly you did not have it when you made your first post. It is therefore inadmissible evidence as to whether your first post was a reasonable thing to write. > Yes he does, If you have decided you want to be an epidemiologist, or at least to learn their skillset, whose responsibility is it to fulfill that desire? I don't think there is a reasonable answer to that other than "mine."
  - throwaway_pdp09 7y ago
    > but if I understand you correctly you did not have it when you made your first post correct > It is therefore inadmissible evidence as to whether your first post was a reasonable thing to write. Completely wrong. I approximated the lowest part of a logistic function with e^x, which is reasonable for small values. Given it matched well with professional epidemiologists' graphs, it suggests I'm getting it approximately right. > whose responsibility is it to fulfill that desire? Mine and yours. Don't stick 'reasonable' on your replies and suppose it insures you in any way cos it doesn't.
    - andrepd 7y ago
      Mate I can start to pontificate randomly about aeronautics design, and you can very well tell me to shut up with no requirement that you are an expert yourself.
    - alien_ 7y ago
      There's a quote that states that all models are wrong, some happen to be useful. With this in mind I think we should stop nitpicking on non-specialists who try to raise awareness of this pandemic. Yes there might be some differences from what a specialist would have done. Due to the speed at which the situation evolves and the inability to test everyone daily there are lots of unknowns so even a specialist may not be able to give a more much precise figure, everything is going to be a rough estimate. This is a very serious situation and it's better to err on the caution side, people's lives depend on everyone doing their part. Non-constructive criticism of people who raise awareness will erode people's buy-in and people will die because of this.

marvin 7y ago

The "behind Italy" number must refer to the number of days after Italy the area reached 100 confirmed cases. Because those numbers obviously don't reflect an extrapolation of the exponential function even 10 days into the future, even corrected for a reduction in the coefficient when numbers grow above 10.000.

hanche 7y ago

You are absolutely right that the early phase of logistic growth is practically indistinguishable from exponential growth. As to what extent this observation is useful when applied to the current situation, I don't know – I am a mathematician, not an epidemiologist. But as a rough guide to aid understanding, I think it probably has some merit.

throwaway_pdp09 7y ago
Thanks, it's nice to have an expert around! I was going to plot the divergence between the two but got seriously despondent and hit the bottle. Trying to sober up now. May I ask, what area do you work in, numerical, discrete, logic, other?