http://www.ccl.net/cca/software/SOURCES/FORTRAN/fit-any-function/fit/fitinstr.shtml
CCL fitinstr.txt
```
The  fit  utility  will  generate,  compile,  link,  and  execute  a
FORTRAN  program to fit a set  of  data points to a user-provided equation
using the SIMPLEX algorithm.   The data points and initial guesses for the
adjustable  parameters  will  be read from a file.   The  equation for the
function  has  to be provided when prompted as a single,  correct  FORTRAN
statement evaluating a variable called YCALC, e.g. :

YCALC = A(1) + A(2)*X(1) + A(3)*X(2)

where the A(i)'s represent the parameters to be determined, and the X(i)'s
the  independent variables.   The equation can be non-linear in either the
parameters  or the variables.   Both the variables and the parameters have
to  be given in the same sequence that they appear in the input file,  and
the  indeces  have  to  be  continuously  increasing, unless refering to a
previously defined variable or parameter, i.e. :

the equation YCALC=A(1)+A(2)*X(1)+A(4)*X(2)       is NOT valid since the
sequence of A's is broken.

the sequence YCALC=A(1)+A(2)*X(1)+(A(1)+A(2))*X(2)             is valid.

the  input  equation  is  terminated by a , thus a single line must be
used.  This line can however be up to 256 characters long and wraps around
when the edge of the screen is reached.  The equation is parsed, converted
to lower case, and  broken  into  all  the necessary FORTRAN lines by this
utility.

The input file should contain in the first line the initial guesses for
the  values  of  all  the  parameters  in  the sequence established by the
indeces assigned in the equation.   The remaining lines should contain the
values  for  all  the  variables  in  the  sequence  of their assignement,
followed by the "observed" value of the dependent variable (Y).  All these
values are read in free format and the program will recognize normal real,
exponential,  or integer numbers as input.  The only requirements are that
all  the  values  for the independent and dependent variables are given in
the  same line for each point, and that they are separated by at least one
blank.   Alphanumeric text or comments can be present and the program will
ignore them.
```
 Modified: Fri Dec 11 17:00:00 1992 GMT Page accessed 4390 times since Sat Apr 17 22:01:38 1999 GMT