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Commit e015b5e5 authored by Ruqian Lyu's avatar Ruqian Lyu
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chang HMM to ong

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......@@ -11,33 +11,7 @@ sequence for the list of SNP markers.
![sscocaller_fig](images/sscocaller_fig.png)
## Hidden Markov Model configuration
- Observations. The allele specific counts across the informative SNP markers for
each chromosome in each sperm cell.
- States. Sperm cells have haploid genomes. There are two possible hidden states (haplotypes)
corresponding to a REF or ALT segment in the haploid genome. At each SNP site $i$,
there are two hidden states: $s_{i}= 0$ corresponds to ALT segment while $s_i=1$
corresponds to REF segment.
- Emission probabilities. Two binomial distributions were used for modelling the
emission probabilities for sperm cells at each SNP marker. For each site $s_i$
$$ c = c_r + c_a ~,$$
$$c_a |_{s = 0} \sim Bin(c,\theta_{ALT} ) ~,$$
$$c_a |_{s = 1}\sim Bin(c,\theta_{REF} ) ~.$$
- Transition Probabilities}. A distance-dependent transition probability [[1]](#1)
was applied, which corresponded to an average of `--cmPmb` cM (centiMorgan) per 1Mb
(1 million base pairs):
$$p_{ij} = 1-e^{(-d_{ij}\mathbf{x}0.5\mathbf{x}10^{-8})} ~,$$
where $p_{ij}$ is the transition probability of transitioning to a different
state at SNP $j$ from SNP $i$, and $d_{ij}$ denotes the physical base-pair
distances between SNP $i$ and SNP $j$.
- Initial probabilities. The initial probabilities for the two hidden states
were set to be both 0.5 since they were equally likely to happen.
![HMM_fig](images/HMM-sscocaller.PNG)
## Inputs
......
images/HMM-sscocaller.PNG

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