!********************************************************************
!* This Program tests Module STATS for basic statistical Functions  *
!* ---------------------------------------------------------------- *
!* SAMPLE RUN:                                                      *
!*                                                                  *
!* Population mean and standard deviation:  0.1288112    0.9453266  *
!*                                                                  *
!* Sample mean and standard deviation:   0.1288112      0.9500890   *
!*                                                                  *
!* For full regression:                                             *
!*              regression coefficients:   4.6191972E-02   2.024592 *
!* standard error of estimate of y on x:    9.522273                *
!*              correlation coefficient:   0.9871089                *
!*                                                                  *
!* For regression forced through (0,0):                             *
!*              regression coefficients:   0.0000000E+00   2.025507 *
!* standard error of estimate of y on x:    9.522309                *
!*              correlation coefficient:   0.9871088                *
!*                                                                  *
!* ---------------------------------------------------------------- *
!* Ref.: "Problem Solving with Fortran 90 By David R.Brooks,        *
!*        Springer-Verlag New York, 1997".                          *
!********************************************************************
Program Tstats

Use Stats

Implicit None  !All variables must be declared

  Real x(500), y(500), avg, std_dev
  Real a, b    !for linear regression y=ax+b
  Real s_yx    !standard error of estimate of y on x
  Real corr    !correlation coefficient
  Integer n    !# of points in array
  Integer i
  
  Data n/100/
  
! Test basic statistics
  Call NormalArray(x,n)
  Call NormalStats(x,n,'p',avg,std_dev)
  
  print *,' '
  print *,' Population mean and standard deviation: ',avg, std_dev
  
  Call NormalStats(x,n,'s',avg,std_dev)       

  print *,' '
  print *,' Sample mean and standard deviation: ',avg, std_dev
  print *,' '

! Test linear regression
  Call NormalArray(y,n)

! Create a linear relationship with 'noise'
  Do i=1,n
    x(i) = i
	y(i) = 2.*i + 10.*y(i)
  End Do
  
! Set a <> zero for full regression analysis
  a=1.
  Call LinearReg(x,y,n,'s',a,b,s_yx,corr)
  
  print *,' For full regression:'
  print *,'              regression coefficients: ', a, b
  print *,' standard error of estimate of y on x: ', s_yx
  print *,'              correlation coefficient: ', corr  	    
  print *,' '

! Set a = zero for full regression forced through (0,0)
  a=0.
  Call LinearReg(x,y,n,'s',a,b,s_yx,corr)
  
  print *,' For regression forced through (0,0):'
  print *,'              regression coefficients: ', a, b
  print *,' standard error of estimate of y on x: ', s_yx
  print *,'              correlation coefficient: ', corr  	    
  print *,' '

End

!end of file tsats.f90