September 2017 Update

Task/Polynomial-regression/REXX/polynomial-regression.rexx

@@ -0,0 +1,51 @@
+/* REXX ---------------------------------------------------------------
+* Implementation of http://keisan.casio.com/exec/system/14059932254941
+*--------------------------------------------------------------------*/
+xl='0 1  2  3  4  5   6   7   8   9  10'
+yl='1 6 17 34 57 86 121 162 209 262 321'
+n=11
+Do i=1 To n
+  Parse Var xl x.i xl
+  Parse Var yl y.i yl
+  End
+xm=0
+ym=0
+x2m=0
+x3m=0
+x4m=0
+xym=0
+x2ym=0
+Do i=1 To n
+  xm=xm+x.i
+  ym=ym+y.i
+  x2m=x2m+x.i**2
+  x3m=x3m+x.i**3
+  x4m=x4m+x.i**4
+  xym=xym+x.i*y.i
+  x2ym=x2ym+(x.i**2)*y.i
+  End
+xm =xm /n
+ym =ym /n
+x2m=x2m/n
+x3m=x3m/n
+x4m=x4m/n
+xym=xym/n
+x2ym=x2ym/n
+Sxx=x2m-xm**2
+Sxy=xym-xm*ym
+Sxx2=x3m-xm*x2m
+Sx2x2=x4m-x2m**2
+Sx2y=x2ym-x2m*ym
+B=(Sxy*Sx2x2-Sx2y*Sxx2)/(Sxx*Sx2x2-Sxx2**2)
+C=(Sx2y*Sxx-Sxy*Sxx2)/(Sxx*Sx2x2-Sxx2**2)
+A=ym-B*xm-C*x2m
+Say 'y='a'+'||b'*x+'c'*x**2'
+Say ' Input  "Approximation"'
+Say ' x   y     y1'
+Do i=1 To 11
+  Say right(x.i,2) right(y.i,3) format(fun(x.i),5,3)
+  End
+Exit
+fun:
+  Parse Arg x
+  Return a+b*x+c*x**2