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1 /* |
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2 |
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3 Copyright (C) 1996, 1997 John W. Eaton |
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4 |
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5 This file is part of Octave. |
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6 |
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7 Octave is free software; you can redistribute it and/or modify it |
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8 under the terms of the GNU General Public License as published by the |
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9 Free Software Foundation; either version 2, or (at your option) any |
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10 later version. |
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11 |
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12 Octave is distributed in the hope that it will be useful, but WITHOUT |
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13 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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15 for more details. |
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16 |
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17 You should have received a copy of the GNU General Public License |
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18 along with Octave; see the file COPYING. If not, write to the Free |
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19 Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
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20 |
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21 */ |
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22 |
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23 // Based on Tony Richardson's filter.m. |
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24 // |
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25 // Originally translated to C++ by KH (Kurt.Hornik@ci.tuwien.ac.at) |
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26 // with help from Fritz Leisch and Andreas Weingessel on Oct 20, 1994. |
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27 // |
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28 // Rewritten to use templates to handle both real and complex cases by |
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29 // jwe, Wed Nov 1 19:15:29 1995. |
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30 |
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31 #ifdef HAVE_CONFIG_H |
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32 #include <config.h> |
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33 #endif |
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34 |
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35 #include "defun-dld.h" |
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36 #include "error.h" |
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37 #include "oct-obj.h" |
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38 |
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39 extern MArray<double> |
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40 filter (MArray<double>&, MArray<double>&, MArray<double>&); |
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41 |
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42 extern MArray<Complex> |
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43 filter (MArray<Complex>&, MArray<Complex>&, MArray<Complex>&); |
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44 |
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45 template <class T> |
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46 MArray<T> |
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47 filter (MArray<T>& b, MArray<T>& a, MArray<T>& x, MArray<T>& si) |
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48 { |
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49 MArray<T> y; |
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50 |
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51 int a_len = a.length (); |
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52 int b_len = b.length (); |
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53 int x_len = x.length (); |
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54 |
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55 int si_len = si.length (); |
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56 |
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57 int ab_len = a_len > b_len ? a_len : b_len; |
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58 |
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59 b.resize (ab_len, 0.0); |
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60 |
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61 if (si.length () != ab_len - 1) |
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62 { |
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63 error ("filter: si must be a vector of length max (length (a), length (b)) - 1"); |
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64 return y; |
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65 } |
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66 |
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67 T norm = a (0); |
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68 |
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69 if (norm == 0.0) |
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70 { |
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71 error ("filter: the first element of a must be non-zero"); |
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72 return y; |
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73 } |
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74 |
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75 y.resize (x_len, 0.0); |
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76 |
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77 if (norm != 1.0) |
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78 b = b / norm; |
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79 |
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80 if (a_len > 1) |
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81 { |
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82 a.resize (ab_len, 0.0); |
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83 |
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84 if (norm != 1.0) |
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85 a = a / norm; |
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86 |
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87 for (int i = 0; i < x_len; i++) |
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88 { |
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89 y (i) = si (0) + b (0) * x (i); |
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90 |
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91 if (si_len > 1) |
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92 { |
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93 for (int j = 0; j < si_len - 1; j++) |
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94 si (j) = si (j+1) - a (j+1) * y (i) |
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95 + b (j+1) * x (i); |
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96 |
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97 si (si_len-1) = b (si_len) * x (i) |
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98 - a (si_len) * y (i); |
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99 } |
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100 else |
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101 si (0) = b (si_len) * x (i) |
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102 - a (si_len) * y (i); |
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103 } |
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104 } |
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105 else if (si_len > 0) |
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106 { |
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107 for (int i = 0; i < x_len; i++) |
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108 { |
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109 y (i) = si (0) + b (0) * x (i); |
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110 |
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111 if (si_len > 1) |
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112 { |
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113 for (int j = 0; j < si_len - 1; j++) |
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114 si (j) = si (j+1) + b (j+1) * x (i); |
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115 |
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116 si (si_len-1) = b (si_len) * x (i); |
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117 } |
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118 else |
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119 si (0) = b (1) * x (i); |
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120 } |
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121 } |
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122 else |
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123 y = b (0) * x; |
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124 |
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125 return y; |
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126 } |
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127 |
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128 extern MArray<double> |
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129 filter (MArray<double>&, MArray<double>&, MArray<double>&, |
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130 MArray<double>&); |
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131 |
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132 extern MArray<Complex> |
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133 filter (MArray<Complex>&, MArray<Complex>&, MArray<Complex>&, |
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134 MArray<Complex>&); |
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135 |
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136 template <class T> |
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137 MArray<T> |
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138 filter (MArray<T>& b, MArray<T>& a, MArray<T>& x) |
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139 { |
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140 int a_len = a.length (); |
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141 int b_len = b.length (); |
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142 |
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143 int si_len = (a_len > b_len ? a_len : b_len) - 1; |
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144 |
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145 MArray<T> si (si_len, T (0.0)); |
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146 |
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147 return filter (b, a, x, si); |
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148 } |
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149 |
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150 DEFUN_DLD (filter, args, , |
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151 "usage: [y [, sf]] = filter (b, a, x [, si])\n\ |
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152 \n\ |
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153 y = filter (b, a, x) returns the solution to the following linear,\n\ |
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154 time-invariant difference equation:\n\ |
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155 \n\ |
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156 a[1] y[n] + ... + a[la] y[n-la+1] = b[1] x[n] + ... + b[lb] x[n-lb+1],\n\ |
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157 where la = length (a) and lb = length (b).\n\ |
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158 \n\ |
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159 [y, sf] = filter (b, a, x, si) sets the initial state of the system, si,\n\ |
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160 and returns the final state, sf. The state vector is a column vector\n\ |
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161 whose length is equal to the length of the longest coefficient vector\n\ |
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162 minus one. If si is not set, the initial state vector is set to all\n\ |
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163 zeros.\n\ |
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164 \n\ |
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165 The particular algorithm employed is known as a transposed Direct Form II\n\ |
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166 implementation.") |
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167 { |
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168 octave_value_list retval; |
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169 |
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170 int nargin = args.length (); |
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171 |
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172 if (nargin < 3 || nargin > 4) |
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173 { |
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174 print_usage ("filter"); |
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175 return retval; |
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176 } |
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177 |
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178 const char *errmsg = "filter: arguments must be vectors"; |
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179 |
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180 int x_is_vector = (args(2).rows () == 1 || args(2).columns () == 1); |
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181 |
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182 int si_is_vector = (nargin == 4 |
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183 && (args(3).rows () == 1 || args(3).columns () == 1)); |
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184 |
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185 if (args(0).is_complex_type () |
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186 || args(1).is_complex_type () |
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187 || args(2).is_complex_type () |
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188 || (nargin == 4 && args(3).is_complex_type ())) |
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189 { |
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190 ComplexColumnVector b = args(0).complex_vector_value (); |
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191 ComplexColumnVector a = args(1).complex_vector_value (); |
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192 ComplexColumnVector x = args(2).complex_vector_value (); |
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193 |
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194 if (! error_state) |
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195 { |
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196 if (nargin == 3) |
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197 { |
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198 ComplexColumnVector y (filter (b, a, x)); |
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199 |
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200 if (x_is_vector) |
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201 retval (0) = octave_value (y, (args(2).columns () == 1)); |
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202 else |
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203 retval (0) = y; |
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204 } |
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205 else |
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206 { |
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207 ComplexColumnVector si = args(3).complex_vector_value (); |
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208 |
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209 if (! error_state) |
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210 { |
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211 ComplexColumnVector y (filter (b, a, x, si)); |
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212 |
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213 if (si_is_vector) |
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214 retval (1) = octave_value (si, (args(3).columns () == 1)); |
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215 else |
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216 retval (1) = si; |
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217 |
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218 if (x_is_vector) |
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219 retval (0) = octave_value (y, (args(2).columns () == 1)); |
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220 else |
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221 retval (0) = y; |
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222 } |
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223 else |
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224 error (errmsg); |
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225 } |
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226 } |
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227 else |
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228 error (errmsg); |
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229 } |
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230 else |
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231 { |
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232 ColumnVector b = args(0).vector_value (); |
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233 ColumnVector a = args(1).vector_value (); |
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234 ColumnVector x = args(2).vector_value (); |
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235 |
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236 if (! error_state) |
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237 { |
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238 if (nargin == 3) |
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239 { |
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240 ColumnVector y (filter (b, a, x)); |
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241 |
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242 if (x_is_vector) |
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243 retval (0) = octave_value (y, (args(2).columns () == 1)); |
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244 else |
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245 retval (0) = y; |
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246 } |
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247 else |
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248 { |
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249 ColumnVector si = args(3).vector_value (); |
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250 |
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251 if (! error_state) |
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252 { |
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253 ColumnVector y (filter (b, a, x, si)); |
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254 |
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255 if (si_is_vector) |
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256 retval (1) = octave_value (si, (args(3).columns () == 1)); |
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257 else |
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258 retval (1) = si; |
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259 |
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260 if (x_is_vector) |
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261 retval (0) = octave_value (y, (args(2).columns () == 1)); |
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262 else |
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263 retval (0) = y; |
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264 } |
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265 else |
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266 error (errmsg); |
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267 } |
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268 } |
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269 else |
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270 error (errmsg); |
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271 } |
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272 |
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273 return retval; |
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274 } |
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275 |
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276 template MArray<double> |
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277 filter (MArray<double>&, MArray<double>&, MArray<double>&, |
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278 MArray<double>&); |
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279 |
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280 template MArray<double> |
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281 filter (MArray<double>&, MArray<double>&, MArray<double>&); |
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282 |
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283 template MArray<Complex> |
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284 filter (MArray<Complex>&, MArray<Complex>&, MArray<Complex>&, |
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285 MArray<Complex>&); |
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286 |
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287 template MArray<Complex> |
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288 filter (MArray<Complex>&, MArray<Complex>&, MArray <Complex>&); |
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289 |
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290 /* |
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291 ;;; Local Variables: *** |
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292 ;;; mode: C++ *** |
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293 ;;; End: *** |
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294 */ |
