* FILE: least-squares.c

* This program computes a linear model for a set of given data.

*

* PROBLEM DEscr iptION:

* The method of least squares is a standard technique used to find

* the equation of a straight line from a set of data. Equation for a

* straight line is given by

*　　 y = mx + b

* where m is the slope of the line and b is the y-intercept.

*

* Given a set of n points {(x1,y1), x2,y2),...,xn,yn)}, let

* SUMx = x1 + x2 + ... + xn

* SUMy = y1 + y2 + ... + yn

* SUMxy = x1*y1 + x2*y2 + ... + xn*yn

* SUMxx = x1*x1 + x2*x2 + ... + xn*xn

*

* The slope and y-intercept for the least-squares line can be

* calculated using the following equations:

* slope (m) = ( SUMx*SUMy - n*SUMxy ) / ( SUMx*SUMx - n*SUMxx )

* y-intercept (b) = ( SUMy - slope*SUMx ) / n

*

* AUTHOR: Dora Abdullah (Fortran version, 11/96)

* REVISED: RYL (converted to C, 12/11/96)- * FILE: least-squares.c

* This program computes a linear model for a set of given data.

*

* PROBLEM DEscr iptION:

*　The method of least squares is a standard technique used to find

*　the equation of a straight line from a set of data. Equation for a

*　straight line is given by

*　　 y = mx + b

*　where m is the slope of the line and b is the y-intercept.

*

*　Given a set of n points {(x1,y1), x2,y2),...,xn,yn)}, let

*　　　SUMx = x1 + x2 + ... + xn

*　　　SUMy = y1 + y2 + ... + yn

*　　　SUMxy = x1*y1 + x2*y2 + ... + xn*yn

*　　　SUMxx = x1*x1 + x2*x2 + ... + xn*xn

*

*　The slope and y-intercept for the least-squares line can be

*　calculated using the following equations:

*　　　　slope (m) = ( SUMx*SUMy - n*SUMxy ) / ( SUMx*SUMx - n*SUMxx )

*　y-intercept (b) = ( SUMy - slope*SUMx ) / n

*

* AUTHOR: Dora Abdullah (Fortran version, 11/96)

* REVISED: RYL (converted to C, 12/11/96)