PROGRAM
$ **********************************************************************
$
$                             L I N R E G
$
$  Program:      LINREG
$
$  Programmer:   Dr. David G. Simpson
$                Department of Physical Science
$                Prince George's Community College
$                Largo, Maryland  20774
$
$  Date:         January 27, 2002
$
$  Language:     Speakeasy
$
$  Description:  This program performs a linear regression analysis for
$                a set of data given as (x,y) pairs.  The output from
$                the program is the slope and y-intercept of the least-
$                squares best fit straight line through the data points.
$
$ **********************************************************************
$
$  Print introductory message
$
" LINREG - Perform linear regression"
"   (Enter X=-9999 to stop data entry and compute linear regression.)"
$
$  Initialize sums
$
N = 0.0
SUMX  = 0.0
SUMX2 = 0.0
SUMXY = 0.0
SUMY  = 0.0
SUMY2 = 0.0
$
$  Start of data entry loop
$
L10:
SPACE(1)
ASK ("Enter X:  ", "X=")
IF (X .EQ. -9999) GOTO L20
ASK ("Enter Y:  ", "Y=")
$
$  Compute sums
$
N = N + 1.0
SUMX  = SUMX + X
SUMX2 = SUMX2 + X * X
SUMXY = SUMXY + X * Y
SUMY  = SUMY + Y
SUMY2 = SUMY2 + Y * Y
GOTO L10
L20:
$
$  Compute slope (M), y-intercept (B), and correlation coefficient (R)
$
M = (N * SUMXY  -  SUMX * SUMY) / (N * SUMX2 - SUMX**2)
B = (SUMY * SUMX2  -  SUMX * SUMXY) / (N * SUMX2  -  SUMX**2)
R = (SUMXY - SUMX * SUMY / N) / SQRT((SUMX2 - SUMX**2/N) *
&  (SUMY2 - SUMY**2/N))
$
$  Print results
$
"Slope        ", M
"y-intercept  ", B
"Correlation  ", R
RETURN
END