15.37  FIT 

FIT [AGAIN[=ON|OFF]]
                                  Coordinate to fit
          [Y|Z]
                                     Type of fit
          [POLYNOMIAL| LEGENDRE| SINE| COSINE| EXPONENTIAL| GAUSSIAN|
          INNVERSE| USER=n| EQUATION "term1;term2;..."]
     [SCALE] [ORDER|TERMS=n] [OFFSET=n]
     [NONLINEAR[=ON|OFF]]
     [COEFFICIENTS|ECOEFFICIENTS|CMINIMUM|CMAXIMUM [INDEX=n] N1,N2,N3...]
          [CONSTRAIN[=ON|OFF]]
     [INCLUDE|EXCLUDE [NONE|EVEN|ODD] [n1,n2...] ]
                                   Data generation
     [CURVE [APPEND[=ON|OFF]] [[X|Y] [FROM xmin] [TO xmax] [BY dx]
          [N=steps]] [BINS|VALUES]] [NAME="name"]
                                   Data selection
     [LIMITED [VLOG[=ON|OFF]] [[FROM]|TO [[X=]nx,[[Y=]ny[,[Z=]nz]]]
          [RECURSOR] [CURSOR] ]
     [POINTS=[FROM] n1 [TO] [n2]]
     [SETS=[FROM] n1 [TO] [n2]]
     [SELECT="name"]
     [MESH[=ON|OFF]]
                                  Output selection
     [LOG[=ON|OFF]] [FULL[=ON|OFF]] [MONITOR[=ON|OFF]]
                                NONLINEAR=ON options
     [ECHISQ=n] [MINUIT] [GRAD[=ON|OFF]] [PRINTLEVEL=n] [REPEAT=n]
          [TOLERANCE=n]

Fits  data  and  optionally  produces  a  curve  containing  the fit.  The
coefficients are typed on the terminal and placed as comments in  the  log
file.  Data points with zero or negative values of DY are omitted from the
fit.  If DY does not exist or is 0.0 for all specified  data  then  DY  is
assumed  to  be  1.0.   If all coefficients are constrained, no fitting is
done, but you may generate the curve  for  those  coefficients.   You  may
subtract the FIT from a data set with the SUBTRACT command.