12.2. - Introduction to the fitting package
The fits are normally run as type-5 user functions, and you should refer to the general description of user functions (the
fn command)
in Chapter 10.
The command-file facility in fit is identical to that
in C-PLOT.
When invoking fits from plot command
files, you can have a separate command file for the fit function,
in which case you would enter from the plot program:
fn fitfunc.5 cmd_file cmd_file_args ...The command file should terminate with an
ex to ensure that
control passes back to the plot program at the end of the command
file.
Alternatively, you can include the fit commands in the C-PLOT command file using the syntax:
fn fitfunc.5 -> ... exAll the commands between the
fn and
ex will be executed
by the fit function.
To continue running the current function you
can use:
fn - ... exThe fits also can be run as independent processes from the shell.
An explanation of the nonlinear least-squares fitting algorithm used in this software, the Marquardt algorithm, can be found in chapter 11 of the book Data Reduction and Error Analysis for the Physical Sciences by Philip R. Bevington (New York, McGraw-Hill, 1969).