def _model_for_L_mer(self, L_mer, gap_index, p_binding_site):
"""
Create a model initialised by this K-mer.
"""
# get the start position of the K-mer and a builder to make the model
mer_len = len(L_mer)
start, builder = self._make_builder(gap_index, mer_len)
# get the emission distribution
nucleo_dist = nucleo_dist_from_mer(
seq_to_numpy(L_mer),
self.options.pseudo_count_for_model_initialisation,
gap_index=gap_index
)
emissions = numpy.ones((self.options.K,4))/4.
emissions[start:start+mer_len+1] = nucleo_dist
# build the model
pssm, in_states, out_states = builder.create(
p_gap=.5,
emissions=emissions
)
model = hmm.as_model(
single_gap.add_to_simple_background_model(
model=pssm,
in_states=in_states,
out_states=out_states,
p_binding_site=p_binding_site
)
)
#print model.A
#from IPython.Debugger import Pdb; Pdb().set_trace();
return model
def _distance_to_passed(self, k_mer):
return min(self.distance(k_mer, seq_to_numpy(other_k_mer)) for other_k_mer in self.passed)
def most_frequent_k_mers(sequences, K, max_to_return):
result = list()
for K_mer, count in yield_k_mers(sequences, K):
if 0 == max_to_return:
break
result.append((K_mer, count))
max_to_return -= 1
return result
if '__main__' == __name__:
#
# Test distance metric between K-mers
#
from gapped_pssms.sequence import seq_to_numpy
distance = K_mer_distance()
K_mers = [
('acgtacgtg', 'gacgtacgt', 1), # 1 shift
('acgtacgtg', 'ggacgtacg', 2), # 2 shifts
('ggacgtacg', 'acgtacgtg', 2), # 2 shifts other way
('aaaaaaaaa', 'aaaaaaaaa', 0), # identical
('aaaaaaaaa', 'ttttttttt', 0), # reverse complement
('acgtacgtc', 'aaaaaaaaa', 7), # very different
]
for k1, k2, d in K_mers:
n1 = seq_to_numpy(k1)
n2 = seq_to_numpy(k2)
assert d == distance(n1, n2) # make sure is correct distance
print '%s - %s : distance=%d' % (k1, k2, d)
assert d == distance(n2, n1) # make sure is symmetrical
def generate_seeds(
sequences,
preprocessed_sequences,
options
):
"""
Generate a list of candidate L-mers and score them to find the best seed L-mer and gap position.
"""
# if we have been given a background model filename and it exists then load it.
if None != options.bg_model_filename and os.path.exists(options.bg_model_filename):
logging.info("Loading supplied background model from %s", options.bg_model_filename)
bg_model = cPickle.load(open(options.bg_model_filename))
converted_seqs = [bg_model.converter.to_order_n(s) for s in sequences]
else:
logging.info("Learning new background model")
bg_model, converted_seqs = learn_bg_model(
sequences,
num_mosaics=options.bg_model_num_mosaics,
order=options.bg_model_order
)
if options.bg_model_filename:
logging.info("Saving background model to %s", options.bg_model_filename)
cPickle.dump(bg_model, open(options.bg_model_filename, 'w'))
if options.force_seed:
logging.info('Forcing seed to be: %s', options.force_seed)
L_mers = [(seq_to_numpy(options.force_seed), len(sequences), len(sequences))]
else:
# Calculate log likelihood of L-mers under background model.
bg_L_mer_scores = calculate_k_mer_scores(bg_model, converted_seqs, options.L)
# Find best candidate L-mers
distance = K_mer_distance(allowed_shifts=options.allowed_shifts, shift_cost=options.shift_cost)
L_mer_seeds = list()
gap_end_offset = options.L/5 + 1
start = time.time()
num_L_mers_to_find = 3 * options.max_L_mers_to_evaluate
logging.info('Finding best %d candidate %d-mers to seed HMM emissions', num_L_mers_to_find, options.L)
L_mers = hmm.top_mers_by_sequence_membership(
preprocessed_sequences,
k=options.L,
n=num_L_mers_to_find
)
logging.info('Finding top %d %d-mers took %f seconds', len(L_mers), options.L, time.time()-start)
if options.force_gap:
logging.info('Forcing gap at position: %d', options.force_gap)
L_mer_seeds = [
(numpy_to_seq(L_mer), L_mer_count, L_mer_num_seqs, options.force_gap, 0.0)
for L_mer, L_mer_count, L_mer_num_seqs in L_mers
]
else:
# Evaluate L-mers
if -1 == options.seed_filter_distance:
min_distance = options.L / 4 + 1
else:
min_distance = options.seed_filter_distance
logging.info('Positioning gaps up to %d bases from end of K-mers', gap_end_offset)
gap_positions = range(gap_end_offset, options.L+1-gap_end_offset)
logging.info('Filtering K-mers that are not %d away from previously evaluated.', min_distance)
logging.info('Evaluating up to %d L-mers.', options.max_L_mers_to_evaluate)
L_mer_filter = DistanceFilter(distance, min_distance=min_distance)
discarded = 0
evaluated = 0
for L_mer, L_mer_count, L_mer_num_seqs in L_mers:
if not L_mer_filter(L_mer) or 4 in L_mer:
logging.debug('Discarding: %s; count: %d; # sequences: %d', numpy_to_seq(L_mer), L_mer_count, L_mer_num_seqs)
discarded += 1
else:
score, gap_index = evaluate_L_mer(L_mer, sequences, bg_L_mer_scores, gap_positions, options)
evaluated += 1
logging.info(
'Evaluated (%3d/%d): %s; gap: %d; count: %d; # sequences: %d; score: %f',
evaluated, options.max_L_mers_to_evaluate, numpy_to_seq(L_mer), gap_index, L_mer_count, L_mer_num_seqs, score
)
L_mer_seeds.append((numpy_to_seq(L_mer), L_mer_count, L_mer_num_seqs, gap_index, score))
if len(L_mer_seeds) == options.max_L_mers_to_evaluate:
break
L_mer_seeds.sort(key=lambda x: -x[4]) # sort by score, highest first
logging.info('Discarded %d L-mers using edit distance', discarded)
logging.info('Evaluated %d L-mers: scores range from %f to %f', evaluated, L_mer_seeds[-1][4], L_mer_seeds[0][4])
return L_mer_seeds, bg_model
