FITANDPLOT module allows data for a property that is dependent on
temperature, or in principle any other variable, to be fitted
automatically to a chosen function. The data comprise a sequence of
pairs of numbers, the independent variable, normally temperature, and
the dependent variable, for example the heat capacity, Cp. The default
function is the conventional four-term Cp function. Although this
handbook refers almost exclusively to fitting of heat capacity, more
general use is not excluded. The data may relate to one or more phases
of a substance. Several facilities are provided to aid in the fitting.
and tabulations make clear exactly what ranges are being fitted
and how well the function compares with the experimental results.
Errors can be checked and amended data stored. Results from fits can be
saved in a format ready to be loaded into a database.
Brief summary of commands
The command DEFINE is used to define and input the data to be fitted.
If the file is in the wrong FORMAT or no file exists then the input
will be aborted.
LIST displays on the screen a numbered list of points,
their weights and splits. Since points are identified by sequence
number it is necessary to list the data to correlate the sequence and
temperatures of individual points.
FIT causes automatic fitting of the data to the
default or chosen FUNCTION to meet the default or chosen TOLERANCE. If
necessary to meet the chosen TOLERANCE, additional ranges are
automatically added. The first and penultimate points are weighted so
as to ensure a good fit between the ranges. Results are rounded
dependent on the function and can be REPORTed to the screen.
CHECK determines any errors in the data by a procedure
for calculating differences. It has several sub-options which control
how errors are detected. Suggested values for error points are shown on
the screen and these can be used with AMEND to effect corrections.
WEIGHT The command WEIGHT is used to weight points
according to their contribution to the fitting. The default weight is 1
for all points except the first and the last for the phase. Where
automatic fitting requires another range the first and last but one
point of each range is weighted to 10 unless a higher weight has been
set manually. The maximum weight allowed is 20. The minimum weight is
SPLIT causes forced splitting of ranges at user defined
split points. The first and penultimate points of the new ranges are
weighted to 10.
AMEND allows the user to amend values of data points
specified by its sequence number.
SAVE_RESULTS saves the results of a fit to a file with default
or chosen format.
STORE stores amended data
STATUS displays the current status of parameters such as
tolerance, function, check order, and the destination of plots.
LASER sends a copy of any diagrams on file to a local
plotting device if available.
takes the user out of FIT_AND_PLOT back to the
runs a macro taken from a file. The name of the file should be
entered in quotes. Commands can also be passed through to the
operating system by prefixing them with a $ (dollar sign). The
dollar sign and operating system command should be entered within
A gentle introduction to using
the options available in COPLOT contains annotated
examples, each directed towards achieving a particular outcome
and shows typical combination of commands which would be necessary
to achieve that end.
A simple summary of the commands
available can also be used as an index to obtain more detailed
help about each command.