## This file is part of mlpy.
## This code is written by Davide Albanese, <albanese@fbk.eu>.
## (C) 2009 Fondazione Bruno Kessler - Via Santa Croce 77, 38100 Trento, ITALY.
## This program is free software: you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation, either version 3 of the License, or
## (at your option) any later version.
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
## You should have received a copy of the GNU General Public License
## along with this program. If not, see <http://www.gnu.org/licenses/>.
__all__ = ['extend']
import numpy as np
def extend(x, method='reflection', length='powerof2'):
"""
Extend the 1D numpy array x beyond its original length.
:Parameters:
x : 1d ndarray
data
method : string ('reflection', 'periodic', 'zeros')
indicates which extension method to use
length : string ('powerof2', 'double')
indicates how to determinate the length
of the extended data
:Returns:
xe : 1d ndarray
extended version of x
Example:
>>> import numpy as np
>>> import mlpy
>>> a = np.array([1,2,3,4,5])
>>> mlpy.extend(a, method='periodic', length='powerof2')
array([1, 2, 3, 4, 5, 1, 2, 3])
"""
if length == 'powerof2':
lt = 2*2**int( np.log2(x.shape[0]))
lp = lt - x.shape[0]
elif length == 'double':
lp = x.shape[0]
else:
ValueError("length %s is not available" % length)
if method == 'reflection':
xret = np.append(x, x[::-1][:lp])
elif method == 'periodic':
xret = np.append(x, x[:lp])
elif method == 'zeros':
xret = np.append(x, np.zeros(lp, dtype=x.dtype))
else:
ValueError("method %s is not available" % method)
return xret
