2 src/math/time-series/arma/innovations.c
4 Copyright (C) 2006 Free Software Foundation, Inc. Written by Jason H. Stover.
6 This program is free software; you can redistribute it and/or modify it under
7 the terms of the GNU General Public License as published by the Free
8 Software Foundation; either version 2 of the License, or (at your option)
11 This program is distributed in the hope that it will be useful, but WITHOUT
12 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
16 You should have received a copy of the GNU General Public License along with
17 this program; if not, write to the Free Software Foundation, Inc., 51
18 Franklin Street, Fifth Floor, Boston, MA 02111-1307, USA.
21 Find preliminary ARMA coefficients via the innovations algorithm.
22 Also compute the sample mean and covariance matrix for each series.
26 P. J. Brockwell and R. A. Davis. Time Series: Theory and
27 Methods. Second edition. Springer. New York. 1991. ISBN
28 0-387-97429-6. Sections 5.2, 8.3 and 8.4.
31 #include <gsl/gsl_matrix.h>
32 #include <gsl/gsl_vector.h>
35 #include <data/case.h>
36 #include <data/casefile.h>
37 #include <libpspp/alloc.h>
38 #include <libpspp/compiler.h>
39 #include <libpspp/message.h>
40 #include <math/coefficient.h>
42 #define _(msgid) gettext (msgid)
45 get_mean_variance (size_t n_vars, const struct casefile *cf,
46 struct innovations_estimate **est)
57 x = xnmalloc (n_vars, sizeof *j);
59 for (n = 0; n < n_vars; n++)
63 est[n]->variance = 0.0;
65 for (r = casefile_get_reader (cf); casereader_read (r, &c);
68 for (n = 0; n < n_vars; n++)
70 if (!mv_is_value_missing (&v->miss, val))
72 tmp = case_data (&c, est[n]->variable->fv);
73 d = (tmp - est[n]->mean) / x[n];
75 est[n]->variance += x[n] * x[n] * d * d;
80 for (n = 0; n < n_vars; n++)
82 est[n]->variance /= x[n];
87 struct innovations_estimate ** pspp_innovations (const struct variable **vars, size_t *n_vars,
88 size_t max_lag, const struct casefile *cf)
90 struct innovations_estimate **est;
95 est = xnmalloc (*n_vars, sizeof *est);
96 for (i = 0; i < *n_vars; i++)
98 if (vars[i]->type == NUMERIC)
100 est[i] = xmalloc (sizeof **est);
101 est[i]->variable = vars[i];
103 est[i]->variance = 0.0;
104 est[i]->cov = gsl_matrix_calloc (max_lag, max_lag);
105 est[i]->coeff = xnmalloc (max_lag, sizeof (*est[i]->coeff));
106 for (j = 0; j < max_lag; j++)
108 est[i]->coeff + j = xmalloc (sizeof (*(est[i]->coeff + j)));
114 msg (MW, _("Cannot compute autocovariance for a non-numeric variable %s"),
115 var_to_string (vars[i]));
120 First data pass to get the mean and variance.
122 get_mean_variance (*n_vars, cf, est);