Add DSP code to filter data, allowing for integration/differentiation

[fw/altos] / ao-tools / lib / cc-period.c

diff --git a/ao-tools/lib/cc-period.c b/ao-tools/lib/cc-period.c
new file mode 100644 (file)
index 0000000..c74cf9d
--- /dev/null
+++ b/ao-tools/lib/cc-period.c
@@ -0,0 +1,64 @@
+/*
+ * Copyright © 2009 Keith Packard <keithp@keithp.com>
+ *
+ * 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; version 2 of the License.
+ *
+ * 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, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+#include "cc.h"
+#include <stdlib.h>
+
+struct cc_perioddata *
+cc_period_make(struct cc_timedata *td, double start_time, double stop_time)
+{
+       int                     len = stop_time - start_time + 1;
+       struct cc_perioddata    *pd;
+       int                     i;
+       double                  prev_time;
+       double                  next_time;
+       double                  interval;
+
+       pd = calloc(1, sizeof (struct cc_perioddata));
+       pd->start = start_time;
+       pd->step = 1;
+       pd->num = len;
+       pd->data = calloc(len, sizeof(double));
+       prev_time = start_time;
+       for (i = 0; i < td->num; i++) {
+               if (start_time <= td->data[i].time && td->data[i].time <= stop_time) {
+                       int     pos = td->data[i].time - start_time;
+
+                       if (i < td->num - 1 && td->data[i+1].time < stop_time)
+                               next_time = (td->data[i].time + td->data[i+1].time) / 2.0;
+                       else
+                               next_time = stop_time;
+                       interval = next_time - prev_time;
+                       pd->data[pos] = td->data[i].value * interval;
+                       prev_time = next_time;
+               }
+       }
+       return pd;
+}
+
+struct cc_perioddata *
+cc_period_low_pass(struct cc_perioddata *raw, double omega_pass, double omega_stop, double error)
+{
+       struct cc_perioddata *filtered;
+
+       filtered = calloc (1, sizeof (struct cc_perioddata));
+       filtered->start = raw->start;
+       filtered->step = raw->step;
+       filtered->num = raw->num;
+       filtered->data = cc_low_pass(raw->data, raw->num, omega_pass, omega_stop, error);
+       return filtered;
+}