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Fit Module Overview

The Fit module is an independent business module at the same level as Form and WorkFlow. It is not part of IndexFit and it does not depend on the thin-film refractive-index fitting workflow.

This module is designed for expression-driven numerical solving. It combines formula editing, parameter fitting, forward calculation, variable inversion, and multi-target optimization in one workspace.

Features at a Glance​

FeatureDescription
Expression ValidationValidate the input expression, referenced variables, referenced coefficients, and unknown identifiers before solving.
Forward CalculationEvaluate function values from the current expression, coefficients, and variable samples.
Coefficient FittingFit unknown coefficients from observed function values.
Target InversionSolve one or more variables from target function values.
Multi-Target OptimizationSolve variables against multiple weighted target expressions.
Result DiagnosticsReview convergence state, iteration counts, residuals, and predicted values in the result window.

Typical Use Cases​

  1. Fit empirical parameters in a custom formula.
  2. Reproduce measured values from a known mathematical model.
  3. Solve process variables from a target output value.
  4. Balance multiple objectives by assigning weights to several target expressions.

Core Concepts​

Expression​

The main expression defines the model to solve, for example:

a * x + b

The module validates this expression before running calculation, fitting, inversion, or optimization.

Coefficients​

Coefficients are adjustable parameters in the expression. Each coefficient can define:

  1. Symbol.
  2. Current value.
  3. Minimum value.
  4. Maximum value.
  5. Whether the coefficient participates in fitting.

Variables​

Variables are bound to business entities instead of being plain temporary strings. Variable entities provide runtime constraints such as:

  1. Default value.
  2. Minimum value.
  3. Maximum value.
  4. Scale.
  5. Unit.

Data Table​

The data table stores:

  1. Calculated values.
  2. Actual values.
  3. One column for each bound variable.

Result Window​

The result window summarizes the latest operation and diagnostics, and for optimization results it can also write solved variables back into the data table.

Accessing the Module​

  1. Navigate to the Fit module from the main application menu.
  2. Open the fit workspace.
  3. Configure expression, coefficients, variables, and data before running operations.
  1. Fit Basic Operations
  2. Editing Table
  3. Floating Window