SciCompMod / memilio

Modular spatio-temporal models for epidemic and pandemic simulations
https://scicompmod.github.io/memilio/
Apache License 2.0
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Add the possibility to simulate phase-type distributed sojourn times in the LCT model #946

Open lenaploetzke opened 4 months ago

lenaploetzke commented 4 months ago

Feature description

By allowing non-identical transition rates between the subcompartments, hypoexponentially distributed sojourn times can be allowed. By adding other possible paths / transitions, one could also represent general phase-type distributions (e.g. allow the path E_1 to E_3 etc.). Phase-type distributions are well suited for approximating general distributions:

As the phase-type distribution is dense in the field of all positive-valued distributions, we can represent any positive valued distribution. (https://en.wikipedia.org/wiki/Phase-type_distribution, have to search for a reliable source)

For this, a general matrix for the transitions between subcompartments might have to be permitted, so that, for example, a flow from E_n to E_1 is also possible (depending on the selected distribution).

See also e.g. P. J. Hurtado und C. Richards, „A procedure for deriving new ode models: Using the generalized linear chain trick to incorporate phase-type distributed delay and dwell time assumptions“, Mathematics in Applied Sciences and Engineering, 2020. https://doi.org/10.5206/mase/10857.

The programming implementation should not be complex. For TimeExposed etc. matrices should be used instead of the ScalarTypes.

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