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Generalise exponential growth distribution as a tilted distribution #6

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SamuelBrand1 opened this issue Aug 30, 2024 · 4 comments
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@SamuelBrand1
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SamuelBrand1 commented Aug 30, 2024

The exponential growth distribution is equivalent to exponentially tilting the $\mathcal{U}(0,1)$ distribution. In general for abs. cont. distributions it changes the pdf from $f(t) \to e^{rt} f(t) / M(r)$ and on the linked wiki page there are some useful distributions where the tilted version is known (e.g. Gamma tilted by $r$ but conditioned onto [0,1] is analytically doable).

@seabbs
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seabbs commented Aug 30, 2024

Good idea

@seabbs seabbs changed the title Possibly generalise exponential growth distribution as a tilted distribution Generalise exponential growth distribution as a tilted distribution Aug 30, 2024
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seabbs commented Aug 31, 2024

@SamuelBrand1 I think you did a bit more exploration of this. Can you throw it up if so?

@seabbs seabbs added enhancement New feature or request help wanted Extra attention is needed labels Sep 2, 2024
@SamuelBrand1
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@SamuelBrand1 I think you did a bit more exploration of this. Can you throw it up if so?

I did a wee thing on if primary time had a reference of (say) truncated Normal on $[0, w_P]$ rather than a uniform then we still get the primary CDF dropping out analytically (because tilted Normal is equivalent to a Normal with shifted params).

The modelling idea here would be combining the concept of certain times in a window being a priori more probable times for a primary event and then combining that with the effect of exponential growth in event incidence.

But I don't know if we want to go forwards with this.

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seabbs commented Sep 20, 2024

Yes I think so

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