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134 lines
4.0 KiB
C++
134 lines
4.0 KiB
C++
#pragma once
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//
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// FILE: Correlation.h
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// AUTHOR: Rob Tillaart
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// VERSION: 0.3.2
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// PURPOSE: Calculate Correlation from a small dataset.
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// URL: https://github.com/RobTillaart/Correlation
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#include "Arduino.h"
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#define CORRELATION_LIB_VERSION (F("0.3.2"))
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class Correlation
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{
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public:
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Correlation(uint8_t size = 20); // WARNING calculate memory usage !!
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~Correlation();
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// returns true if the pair of values is added to internal array.
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// returns false when internal array is full.
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bool add(float x, float y);
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// administrative functions
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uint8_t count() { return _count; };
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uint8_t size() { return _size; };
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void clear();
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// in running mode, adding new pair of values will replace old ones
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// this constantly adapts the regression parameters A and B (iff calculate is called)
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void setRunningCorrelation(bool rc) { _runningMode = rc; };
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bool getRunningCorrelation() { return _runningMode; };
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// worker, to calculate the correlation parameters.
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// MUST be called before retrieving the parameters
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// A, B, R, Rsquared, Esquared, avgX and avgY
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//
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// parameter forced overrules the _needRecalculate flag.
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// forced is default false to maintain backwards compatibility
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//
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// returns false if contains no elements ==> count() == 0
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bool calculate(bool forced = false);
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// enables / disables R, Rsquared and Esquared calculation
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// This can be used to speed up the calculate function if
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// these values are not used in your project.
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void setR2Calculation(bool doR2) { _doR2 = doR2; };
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bool getR2Calculation() { return _doR2; };
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void setE2Calculation(bool doE2) { _doE2 = doE2; };
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bool getE2Calculation() { return _doE2; };
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// Y = A + B * X
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// note if no elements are added or calculate is not called
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// the values for A and B are 0
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float getA() { return _a; };
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float getB() { return _b; };
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// getR() returns correlation coefficient (0.2.0 fixed sign)
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float getR() { return _r; };
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float getRsquare() { return _r * _r; };
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// returns sum of the errors squared == indication of 'spread'
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// the smaller this value the more the points are on/near one line.
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float getEsquare() { return _sumErrorSquare; };
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// get the average values of the datasets (if count > 0)
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float getAverageX() { return _avgX; }; // will replace getAvgX() in time
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float getAverageY() { return _avgY; }; // will replace getAvgY() in time
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// float getAvgX() { return _avgX; }; // obsolete in 0.3.0
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// float getAvgY() { return _avgY; }; // obsolete in 0.3.0
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// based on the dataset get the estimated values for X and Y
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// it uses the last calculated A and B
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// library does not return a confidence interval for these values.
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float getEstimateY(float x);
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float getEstimateX(float y);
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// STATISTICAL
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// to get bounding box of all x,y pairs.
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float getMinX(); // idem
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float getMaxX(); // idem
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float getMinY(); // idem
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float getMaxY(); // idem
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// DEBUGGING - access to internal arrays.
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bool setXY(uint8_t index, float x, float y); // returns true if succeeded
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bool setX(uint8_t index, float x); // returns true if succeeded
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bool setY(uint8_t index, float y); // returns true if succeeded
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float getX(uint8_t index); // idem
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float getY(uint8_t index); // idem
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float getSumXY(); // replaces getSumXiYi()
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float getSumX2(); // replaces getSumXi2()
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float getSumY2(); // replaces getSumYi2()
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private:
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uint8_t _size = 0;
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uint8_t _index = 0;
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uint8_t _count = 0;
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bool _runningMode = false;
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bool _needRecalculate = true;
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bool _doE2 = true;
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bool _doR2 = true;
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float * _x;
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float * _y;
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float _avgX;
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float _avgY;
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float _a;
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float _b;
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float _div_b;
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float _r;
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float _sumErrorSquare;
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float _sumXiYi;
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float _sumXi2;
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float _sumYi2;
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};
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// -- END OF FILE --
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