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Result for the “BFGS” method for the 1989-1990 epidemic (5 parameters, alpha values are equal to 1/7 for both the models):

Weston: Setting the alpha values to 1/7, is not correct. Perhaps I'll try again with them equal to around one.

For the guess of parameters beta1 = 0.3 Ne = 1377 I1 = 1 beta2 = 0.3 I2 = 1, we obtained

beta1 = 0.3119233 Ne = 1146.8615307 I1 = 4.0274121 beta2 = 0.7378440 I2 = 10.9647797

So, this implies that f = 1146.8615307/27653146 = 0.00004147309

The covariance matrix was

            [,1]          [,2]         [,3]          [,4]         [,5]

[1,] 8.229108e-04 -0.0001365216 -0.063265298 6.507124e-05 -0.002995546 [2,] -1.365216e-04 -0.9551443153 0.030190859 4.924638e-04 -0.035797595 [3,] -6.326530e-02 0.0301908588 5.682782704 9.745016e-03 -0.517095458 [4,] 6.507124e-05 0.0004924638 0.009745016 7.720312e-04 -0.047579524 [5,] -2.995546e-03 -0.0357975946 -0.517095458 -4.757952e-02 3.450704600

The MLE was 3996.859

Here’s a plot of the model with the data (red is the data, blue is the sum of the two models, green is the lamb2 model, and purple is the lamb1 model)

7_.pdf

Weston: This does not give a good model.


Junling: Yes, but that means the infectious period is 7 weeks, that cannot be right. You might want to set it to 5/7 or 1.