Simulate an alignment#
Section author: Gavin Huttley
For this example we just create a simple model using a four taxon tree with different branch lengths and a Felsenstein model.
import sys
from cogent3 import make_tree
from cogent3.evolve.models import get_model
Specify the 4 taxon tree,
t = make_tree("(a:0.4,b:0.3,(c:0.15,d:0.2)edge.0:0.1);")
Define our Felsenstein 1981 substitution model.
sm = get_model("F81")
lf = sm.make_likelihood_function(t)
lf.set_constant_lengths()
lf.set_motif_probs(dict(A=0.1, C=0.2, G=0.3, T=0.4))
lf
F81
number of free parameters = 0
| edge | parent | length |
|---|---|---|
| a | root | 0.4000 |
| b | root | 0.3000 |
| c | edge.0 | 0.1500 |
| d | edge.0 | 0.2000 |
| edge.0 | root | 0.1000 |
| A | C | G | T |
|---|---|---|---|
| 0.1000 | 0.2000 | 0.3000 | 0.4000 |
We’ll now create a simulated alignment of length 1000 nucleotides.
simulated = lf.simulate_alignment(sequence_length=1000)
simulated
| 0 | |
| a | AGTTTTTCTGGTTCCGTGTTTCATTGGTCTAATGCTTGCGCCGGACTGGCCGGCTGGTTG |
| b | G....G..G.T..GT....G.T..CT...CC..T.C.T..G..A..G.CT.TATG.C... |
| c | TC..AA..GT...GTC..CG.T.A.TC..C...C.G.T..G..A..G..TT.AA.T.G.T |
| d | TC.G.A..GT..GGTC...G.T.A.T...C...T.C.T..T..AG.G..TTTTAC..G.T |
4 x 1000 (truncated to 4 x 60) dna alignment