JAVA实现的一元线性回归 LINEAR REGRESSION

package src; /** * A least-squares regression line function. */ import java.util.*; import java.math.BigDecimal; public class RegressionLine //implements Evaluatable { /** sum of x */ private double sumX; /** sum of y */ private double sumY; /** sum of x*x */ private double sumXX; /** sum of x*y */ private double sumXY; /** sum of y*y */ private double sumYY; /** sum of yi-y */ private double sumDeltaY; /** sum of sumDeltaY^2 */ private double sumDeltaY2; /**误差 */ private double sse; private double sst; private double E; private String[] xy ; private ArrayList listX ; private ArrayList listY ; private int XMin,XMax,YMin,YMax; /** line coefficient a0 */ private float a0; /** line coefficient a1 */ private float a1; /** number of data points */ private int pn ; /** true if coefficients valid */ private boolean coefsValid; /** * Constructor. */ public RegressionLine() { XMax = 0; YMax = 0; pn = 0; xy =new String[2]; listX = new ArrayList(); listY = new ArrayList(); } /** * Constructor. * @param data the array of data points */ public RegressionLine(DataPoint data[]) { pn = 0; xy =new String[2]; listX = new ArrayList(); listY = new ArrayList(); for (int i = 0; i < data.length; ++i) { addDataPoint(data[i]); } } /** * Return the current number of data points. * @return the count */ public int getDataPointCount() { return pn; } /** * Return the coefficient a0. * @return the value of a0 */ public float getA0() { validateCoefficients(); return a0; } /** * Return the coefficient a1. * @return the value of a1 */ public float getA1() { validateCoefficients(); return a1; } /** * Return the sum of the x values. * @return the sum */ public double getSumX() { return sumX; } /** * Return the sum of the y values. * @return the sum */ public double getSumY() { return sumY; } /** * Return the sum of the x*x values. * @return the sum */ public double getSumXX() { return sumXX; } /** * Return the sum of the x*y values. * @return the sum */ public double getSumXY() { return sumXY; } public double getSumYY() { return sumYY; } public int getXMin() { return XMin; } public int getXMax() { return XMax; } public int getYMin() { return YMin; } public int getYMax() { return YMax; } /** * Add a new data point: Update the sums. * @param dataPoint the new data point */ public void addDataPoint(DataPoint dataPoint) { sumX += dataPoint.x; sumY += dataPoint.y; sumXX += dataPoint.x*dataPoint.x; sumXY += dataPoint.x*dataPoint.y; sumYY += dataPoint.y*dataPoint.y; if(dataPoint.x > XMax){ XMax = (int)dataPoint.x; } if(dataPoint.y > YMax){ YMax = (int)dataPoint.y; } //把每个点的具体坐标存入ArrayList中，备用 xy[0] = (int)dataPoint.x+ ""; xy[1] = (int)dataPoint.y+ ""; if(dataPoint.x!=0 && dataPoint.y != 0){ System.out.print(xy[0]+","); System.out.println(xy[1]); try{ //System.out.println("n:"+n); listX.add(pn,xy[0]); listY.add(pn,xy[1]); } catch(Exception e){ e.printStackTrace(); } /* System.out.println("N:" + n); System.out.println("ArrayList listX:"+ listX.get(n)); System.out.println("ArrayList listY:"+ listY.get(n)); */ } ++pn; coefsValid = false; } /** * Return the value of the regression line function at x. * (Implementation of Evaluatable.) * @param x the value of x * @return the value of the function at x */ public float at(int x) { if (pn < 2) return Float.NaN; validateCoefficients(); return a0 + a1*x; } public float at(float x) { if (pn < 2) return Float.NaN; validateCoefficients(); return a0 + a1*x; } /** * Reset. */ public void reset() { pn = 0; sumX = sumY = sumXX = sumXY = 0; coefsValid = false; } /** * Validate the coefficients. * 计算方程系数 y=ax+b 中的a */ private void validateCoefficients() { if (coefsValid) return; if (pn >= 2) { float xBar = (float) sumX/pn; float yBar = (float) sumY/pn; a1 = (float) ((pn*sumXY - sumX*sumY) /(pn*sumXX - sumX*sumX)); a0 = (float) (yBar - a1*xBar); } else { a0 = a1 = Float.NaN; } coefsValid = true; } /** * 返回误差 */ public double getR(){ //遍历这个list并计算分母 for(int i = 0; i < pn -1; i++) { float Yi= (float)Integer.parseInt(listY.get(i).toString()); float Y = at(Integer.parseInt(listX.get(i).toString())); float deltaY = Yi - Y; float deltaY2 = deltaY*deltaY; /* System.out.println("Yi:" + Yi); System.out.println("Y:" + Y); System.out.println("deltaY:" + deltaY); System.out.println("deltaY2:" + deltaY2); */ sumDeltaY2 += deltaY2; //System.out.println("sumDeltaY2:" + sumDeltaY2); } sst = sumYY - (sumY*sumY)/pn; //System.out.println("sst:" + sst); E =1- sumDeltaY2/sst; return round(E,4) ; } //用于实现精确的四舍五入 public double round(double v,int scale){ if(scale<0){ throw new IllegalArgumentException( "The scale must be a positive integer or zero"); } BigDecimal b = new BigDecimal(Double.toString(v)); BigDecimal one = new BigDecimal("1"); return b.divide(one,scale,BigDecimal.ROUND_HALF_UP).doubleValue(); } public float round(float v,int scale){ if(scale<0){ throw new IllegalArgumentException( "The scale must be a positive integer or zero"); } BigDecimal b = new BigDecimal(Double.toString(v)); BigDecimal one = new BigDecimal("1"); return b.divide(one,scale,BigDecimal.ROUND_HALF_UP).floatValue(); } }