FITTER Add-In for Excel
FITTER is a powerful instrument of statistical analysis. Using it you may solve multivariate
nonlinear regression problems. Much of the power of FITTER comes from its ability
to estimate parameter values of complicated user-defined functions that may
be entered in ordinary algebraic notation as a set of explicit, implicit
and ordinary differential equations. FITTER uses the unique procedure for analytic
calculation of derivatives and special optimization algorithm which
provides the high accuracy even for significantly nonlinear models. All complicated
calculations are performed in the special DLL library created using C++
compiler, which provides high speed processing.
- What is FITTER?
- FITTER is an Add-In procedure for Excel. If you are under Excel you can open FITTER as
any add-in file using Tools/Add-Ins menu command. It will add the new
menu item Fitter into Tools menu. Clicking it will activate main Fitter dialog for starting FITTER.
FITTER allows to include prior knowledge about parameters and accuracy of measurement
in addition to experimental data. Using Bayesian estimation, you can process
both unlimited arrays of single-response data, and data referring to different responses.
With the help of FITTER you can obtain a lot of additional statistical information
concerning the input data and the quality of fitting. Parameter estimates, variances,
covariance matrix, correlation matrix and F-matrix; the starting and final values of the
sum of squares and objective function, error variance, and spread in eigenvalues of the
Hessian matrix; error variance for each observation point calculated by fit and by
Moreover, there are hypotheses testing for: Student's test for outliers,
test of series for residual correlation, Bartlett's test for homoscedastisity, Fisher's
test for goodness of fit. Also, you can calculate confidence intervals for
each observation point by linearization method or with the help of modified bootstrap
- FITTER Approach
- FITTER takes all information from open Excel workbook. Information should be placed
directly on a worksheets (Data and Parameters) or written in a text box (Model). All
results are also output as tables on the worksheets. In purpose to explain what
information you want to use, you need to register it with the help of FITTER wizards. There are DATA, MODEL and BAYES registration
wizards. While working with different FITTER wizards you only register the required
information, change options and look through process of registration. You may change data
only on the worksheets but not inside the wizards. Since your information (Data, Model,
...) has been registered it is kept in memory till you replace it by another registration.
If you want to do some changes within the registered range of information, just write them
on the worksheet. You need not register it again. Look through Example
to understand FITTER approach.
- FITTER Functions
- All FITTER operations which are performed with the help of wizards may be done using
Fitter functions too. For example, Data registration is performed by the
Here sDataRange is the reference to the Data range, sCodeString is
the code string explaining the sense of columns in the Data range (P for
"predictor", R for "response" and so on). If you are
accustomed with VBA programming, open new Excel module and write there the desired
proceedings of function. Examples may be found in Fitter Applications.
- FITTER Limits and Requirements
- The following is a summary of FITTER limitations
- Works only with single-response models.
- Maximum length of variable name = 15 characters
- Maximum length of numeric constants = 15 characters (in the model text box)
- Maximum length of data values and parameter values (in the worksheet tables) = 39
The maximum number of predictors, parameters, equations in the Model and data
observations that FITTER can handle is limited only by the memory space provided by your
system and by capacity of your computer to process complicated (multi-step) models.
FITTER can not use models containing circular interconnections of variables.
- Minimum requirements to run FITTER for Windows are:
- 486DX (floating point coprocessor required)
- 8 MB RAM
- 3 MB free hard-disk space
- Microsoft Windows 95
- Excel 7.0
- FITTER and Other NLR Tools
- We made an attempt to compare FITTER with various software tools that have been designed
for non-linear regression analysis. Of course we are biased, but you can download compare.zip file that contains Word 6.0 document and
understand our point of view.
- See more
- Return to Polycert Main Page.
Last revision 26 August 2002