summaryrefslogtreecommitdiff
path: root/thirdparty/etc2comp/EtcMath.cpp
diff options
context:
space:
mode:
Diffstat (limited to 'thirdparty/etc2comp/EtcMath.cpp')
-rw-r--r--thirdparty/etc2comp/EtcMath.cpp64
1 files changed, 64 insertions, 0 deletions
diff --git a/thirdparty/etc2comp/EtcMath.cpp b/thirdparty/etc2comp/EtcMath.cpp
new file mode 100644
index 0000000000..096d5f7ab9
--- /dev/null
+++ b/thirdparty/etc2comp/EtcMath.cpp
@@ -0,0 +1,64 @@
+/*
+ * Copyright 2015 The Etc2Comp Authors.
+ *
+ * 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 "EtcConfig.h"
+#include "EtcMath.h"
+
+namespace Etc
+{
+
+ // ----------------------------------------------------------------------------------------------------
+ // calculate the line that best fits the set of XY points contained in a_afX[] and a_afY[]
+ // use a_fSlope and a_fOffset to define that line
+ //
+ bool Regression(float a_afX[], float a_afY[], unsigned int a_Points,
+ float *a_fSlope, float *a_fOffset)
+ {
+ float fPoints = (float)a_Points;
+
+ float fSumX = 0.0f;
+ float fSumY = 0.0f;
+ float fSumXY = 0.0f;
+ float fSumX2 = 0.0f;
+
+ for (unsigned int uiPoint = 0; uiPoint < a_Points; uiPoint++)
+ {
+ fSumX += a_afX[uiPoint];
+ fSumY += a_afY[uiPoint];
+ fSumXY += a_afX[uiPoint] * a_afY[uiPoint];
+ fSumX2 += a_afX[uiPoint] * a_afX[uiPoint];
+ }
+
+ float fDivisor = fPoints*fSumX2 - fSumX*fSumX;
+
+ // if vertical line
+ if (fDivisor == 0.0f)
+ {
+ *a_fSlope = 0.0f;
+ *a_fOffset = 0.0f;
+ return true;
+ }
+
+ *a_fSlope = (fPoints*fSumXY - fSumX*fSumY) / fDivisor;
+ *a_fOffset = (fSumY - (*a_fSlope)*fSumX) / fPoints;
+
+ return false;
+ }
+
+ // ----------------------------------------------------------------------------------------------------
+ //
+
+} // namespace Etc