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** File: TPSht_01.hlp
** Index: 40
** More Sheet View Help
:: Interpolation commands
:: Fitting commands
█ Interpolation
The Math | Interpolate menu item
contains a pop-up menu which contains the
data interpolation commands.
█ Polynomial
This command interpolates the selected
X-Y columns by a polynomial of degree
n-1, where n is the number of valid data
points of X-Y columns.
█ Rational
This command interpolates the selected
X-Y columns by a rational function of
degree K-1, where K is the number of
valid data points of X-Y columns.
█ Natural Spline
This command interpolates data using
a natural cubic polynomials between each
successive pair of nodes.
█ Clamped Spline
This command interpolates the selected
X-Y columns by a clamped cubic spline.
The boundary conditions are given in a
way such that the third derivatives are
continuous.
█ Stineman
This command interpolates the selected
X-Y columns by a Stineman function.
The Stineman function consists of
piecewise diagonal rational functions
of order 3 (i.e. the degree of
numerator polynomial is 2 and the
degree of denominator polynomial is 1).
These rational functions are to have
continuity up to first derivative.
█ Fitting
This menu item contains six fitting
commands. The first five commands are
linear in terms of the parameters
appearing in the pre-defined function form.
The last command is for user-defined
non-linear parameter fitting.
█ Line: a*x+b
This command fits the selected x-y
data by a straight line.
█ Power: a*x^b
This command fits the selected x-y
data by a power function.
█ Exp: a*exp(b*x)
This command fits the selected x-y
data by a mono-exponential function.
█ Polynomial
This command fits the selected x-y
data by a polynomial
█ Spline
This command fits the selected x-y
data by a natural cubic spline.
█ User Defined
This command performs non-linear
curve fitting. It displays the Fitting
dialog box. In this dialog box, you can
type in a model or load/save a model
from/to disk. The model file format
are described in Section 6.4.2. In the
model equations, you can have up to 10
independent variables, 10 dependent
variables, and 10 parameters. This means
you can do 3D curve fitting easily with
the Math | Fitting - User-Define command.
See TpSht_09.hlp (Index: 48) on TechPlot's
model equation convention.