Separating burn probabilities from transition probabilities

[crosbya1]

I know this is a very beginner question, but I just want to make sure I’m doing something correctly. Until now, I’ve been doing fire transitions the same way they are shown in the Introductory course, where the transition probability from state class A to state class B from fire is the product of the burn probability and the probability of transitioning to state class B given that it burned (or at least that’s how I interpret it). What I want to do now is set baseline burn probabilities for each state class, and then give them probabilities of transitioning to other state classes, given burning, separately in the transition probabilities table. I did this by specifying the burn probabilities as multipliers, e.g.:
| State Class | Transition Type/Group | Multiplier |
| coniferous:all | Fire[type] | 0.0050 |
| deciduous:all | Fire[type] | 0.0001 |

and in the transition probabilities table, e.g.:
| Class | To Class | Transition Type | Probability |
| coniferous:all | coniferous:all | Fire[type] | 0.7500 |
| coniferous:all | deciduous:all | Fire[type] | 0.2500 |

I think this works right, but I’m hoping for some confirmation.
As a side question (if this is correct), what does st-sim do if the transition probabilities don’t add to 1? I tried that and it ran just fine.

[leonardo-frid]

Hi crosbya1,

The approach you show above should work just fine.

With respect to your question about what happens when probabilities exceed 1, in your case case lets say that for the second table for transition pathways you provided values that add up to 1.15 instead of 1.0:
| Class | To Class | Transition Type | Probability |
| coniferous:all | coniferous:all | Fire[type] | 0.9000 |
| coniferous:all | deciduous:all | Fire[type] | 0.2500 |

Instead of a realized transition probability for Fire[type] in coniferous:all of 0.0050 you would see a realized probability of 0.0050 * 1.15 = 0.00575

Hope that helps!
Leonardo

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