# Source code for deltasigma._padl

# -*- coding: utf-8 -*-
# _padl.py
# This module provides the padl function.
# Copyright 2013 Giuseppe Venturini
# This file is part of python-deltasigma.
#
# python-deltasigma is a 1:1 Python replacement of Richard Schreier's
# MATLAB delta sigma toolbox (aka "delsigma"), upon which it is heavily based.
# The delta sigma toolbox is (c) 2009, Richard Schreier.
#
# python-deltasigma 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
# LICENSE file for the licensing terms.
"""This module provides the padl() function, which pads a matrix on the
left.
"""
import numpy as np
[docs]def padl(x, n, val=0.):
"""Pad a matrix ``x`` on the left to length ``n`` with value ``val``.
**Parameters:**
x : ndarray
The matrix to be padded.
n : int
The number of columns of the matrix after padding.
val : scalar, optional
The value to be used used for padding.
.. note:: A 1-d array, for example ``a.shape == (N,)`` is reshaped to be
a 1 row array: ``a.reshape((1, N))``
The empty matrix is assumed to be have 1 empty row.
**Returns:**
xp : 2-d ndarray
The padded matrix.
"""
if len(x.shape) == 1:
xp = x.reshape((1, x.shape[0]))
else:
xp = x
y = np.concatenate((
val*np.ones((xp.shape[0], n - xp.shape[1])),
xp
), axis=1)
return y