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Diffstat (limited to 'thirdparty/etc2comp/EtcMath.cpp')
-rw-r--r-- | thirdparty/etc2comp/EtcMath.cpp | 64 |
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 |