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functions in fitlsq.i - f


             yp= fitlsq(y, x, xp)  
             yfit= interp(yp, xp, xfit)  
     performs a least squares fit to the data points (X, Y).  The input  
     XP are the abcissas of the piecewise linear function passing through  
     (XP, YP) which is the best fit to the data (X,Y) in a least squares  
     sense.  The XP must be strictly monotone, either increasing or  
     decreasing.  As for interp, the piecewise linear fit is taken to be  
     constant outside the limits of the XP.  
     The result YP is linearly interpolated through any consecutive  
     intervals of XP which contain no data points X, and linearly  
     extrapolated beyond the extreme values of X (if any of the intervals  
     of XP lie outside these extremes).  
     A WEIGHT keyword of the same length as X and Y may be supplied in  
     order to weight the various data points differently; a typical  
     WEIGHT function is 1/sigma^2 where sigma are the standard deviations  
     associated with the Y values.  
interpreted function, defined at i/fitlsq.i   line 10  
SEE ALSO: interp