1 files changed, 57 insertions, 0 deletions
diff --git a/media/mca/filterfw/native/core/statistics.cpp b/media/mca/filterfw/native/core/statistics.cpp
new file mode 100644
index 0000000..6f7fee7
--- /dev/null
+++ b/media/mca/filterfw/native/core/statistics.cpp
@@ -0,0 +1,57 @@
+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "core/statistics.h"
+
+#include <math.h>
+
+namespace android {
+namespace filterfw {
+
+IncrementalGaussian::IncrementalGaussian()
+    : n_(0),
+      sum_x_(0.0f),
+      sum_x2_(0.0f),
+      mean_(0.0f),
+      var_(0.0f),
+      exp_denom_(0.0f),
+      pdf_denom_(0.0f) {
+}
+
+void IncrementalGaussian::Add(float value) {
+  ++n_;
+  sum_x_ += value;
+  sum_x2_ += value * value;
+
+  mean_ = sum_x_ / n_;
+  var_ = sum_x2_ / n_ - mean_ * mean_;
+
+  exp_denom_ = 2.0f * var_;
+  pdf_denom_ = sqrtf(M_PI * exp_denom_);
+}
+
+float IncrementalGaussian::Std() const {
+  return sqrtf(var_);
+}
+
+float IncrementalGaussian::Pdf(float value) const {
+  if (var_ == 0.0f) { return n_ > 0 ? value == mean_ : 0.0f; }
+  const float diff = value - mean_;
+  return expf(-diff * diff / exp_denom_) / pdf_denom_;
+}
+
+} // namespace filterfw
+} // namespace android