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# Module containing several function to load and transform spike trains
# Copyright 2014, Mario Mulansky <mario.mulansky@gmx.net>
# Distributed under the BSD License
import numpy as np
from pyspike import SpikeTrain
############################################################
# spike_train_from_string
############################################################
def spike_train_from_string(s, edges, sep=' ', is_sorted=False):
""" Converts a string of times into a :class:`.SpikeTrain`.
:param s: the string with (ordered) spike times.
:param edges: interval defining the edges of the spike train.
Given as a pair of floats (T0, T1) or a single float T1,
where T0=0 is assumed.
:param sep: The separator between the time numbers, default=' '.
:param is_sorted: if True, the spike times are not sorted after loading,
if False, spike times are sorted with `np.sort`
:returns: :class:`.SpikeTrain`
"""
return SpikeTrain(np.fromstring(s, sep=sep), edges, is_sorted)
############################################################
# load_spike_trains_txt
############################################################
def load_spike_trains_from_txt(file_name, edges,
separator=' ', comment='#', is_sorted=False,
ignore_empty_lines=True):
""" Loads a number of spike trains from a text file. Each line of the text
file should contain one spike train as a sequence of spike times separated
by `separator`. Empty lines as well as lines starting with `comment` are
neglected. The `edges` represents the start and the end of the
spike trains.
:param file_name: The name of the text file.
:param edges: A pair (T_start, T_end) of values representing the
start and end time of the spike train measurement
or a single value representing the end time, the
T_start is then assuemd as 0.
:param separator: The character used to seprate the values in the text file
:param comment: Lines starting with this character are ignored.
:param sort: If true, the spike times are order via `np.sort`, default=True
:returns: list of :class:`.SpikeTrain`
"""
spike_trains = []
spike_file = open(file_name, 'r')
for line in spike_file:
if len(line) > 1 and not line.startswith(comment):
# use only the lines with actual data and not commented
spike_train = spike_train_from_string(line, edges,
separator, is_sorted)
spike_trains.append(spike_train)
return spike_trains
############################################################
# merge_spike_trains
############################################################
def merge_spike_trains(spike_trains):
""" Merges a number of spike trains into a single spike train.
:param spike_trains: list of :class:`.SpikeTrain`
:returns: spike train with the merged spike times
"""
# get the lengths of the spike trains
lens = np.array([len(st.spikes) for st in spike_trains])
merged_spikes = np.empty(np.sum(lens))
index = 0 # the index for merged_spikes
indices = np.zeros_like(lens) # indices of the spike trains
index_list = np.arange(len(indices)) # indices of indices of spike trains
# that have not yet reached the end
# list of the possible events in the spike trains
vals = [spike_trains[i].spikes[indices[i]] for i in index_list]
while len(index_list) > 0:
i = np.argmin(vals) # the next spike is the minimum
merged_spikes[index] = vals[i] # put it to the merged spike train
i = index_list[i]
index += 1 # next index of merged spike train
indices[i] += 1 # next index for the chosen spike train
if indices[i] >= lens[i]: # remove spike train index if ended
index_list = index_list[index_list != i]
vals = [spike_trains[n].spikes[indices[n]] for n in index_list]
return SpikeTrain(merged_spikes, [spike_trains[0].t_start,
spike_trains[0].t_end])
############################################################
# generate_poisson_spikes
############################################################
def generate_poisson_spikes(rate, interval):
""" Generates a Poisson spike train with the given rate in the given time
interval
:param rate: The rate of the spike trains
:param interval: A pair (T_start, T_end) of values representing the
start and end time of the spike train measurement or
a single value representing the end time, the T_start
is then assuemd as 0. Auxiliary spikes will be added
to the spike train at the beginning and end of this
interval, if they are not yet present.
:type interval: pair of doubles or double
:returns: Poisson spike train as a :class:`.SpikeTrain`
"""
try:
T_start = interval[0]
T_end = interval[1]
except:
T_start = 0
T_end = interval
# roughly how many spikes are required to fill the interval
N = max(1, int(1.2 * rate * (T_end-T_start)))
N_append = max(1, int(0.1 * rate * (T_end-T_start)))
intervals = np.random.exponential(1.0/rate, N)
# make sure we have enough spikes
while T_start + sum(intervals) < T_end:
# print T_start + sum(intervals)
intervals = np.append(intervals,
np.random.exponential(1.0/rate, N_append))
spikes = T_start + np.cumsum(intervals)
spikes = spikes[spikes < T_end]
return SpikeTrain(spikes, interval)
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