Manual Fitting Mode

This tutorial introduces the manual mode, which allows you to visualize the effect of a formula and manually adjust its parameters using sliders — without launching an automatic fit. This mode is ideal for verifying formulas, exploring parameter behavior, and setting good initial guesses.

Step 1 – Load the data

Use File > Load Data and select:

examples/data/manual_fit_tuto.csv

This dataset includes:

  • X: the main sweep variable
  • Y: a secondary index (discrete)
  • Z: the observed value for each (X, Y)

After loading, the application automatically enters Fit per Y and displays a set of curves indexed by Y.

There is no manual mode for 3d plots

Step 2 – Switch to manual mode

In the Fit Control dock, click:

Manual

This disables the "Fit" button and instead activates a slider interface for parameter adjustment. This allows real-time manipulation of parameters without optimization.

Step 3 – Define a formula

Try the following example:

z = A * sin(B * x + C) + D * y

Once entered, sliders appear for each parameter (A, B, C, D). You can now adjust them manually.

  • Use the slider to change the value of the parameter
  • The limits can be changed by clicking on the values at the ends of the sliders

Step 4 – Adjust the sliders

Each slider updates the plot in real time. You can:

  • See how each parameter influences the curve
  • Explore how well the formula matches the data visually
  • Zoom/pan to inspect features in detail

If in 2D mode (i.e. Y is present), a curve is displayed for each value of Y.

Manual mode sliders

Step 5 – Use it to set initial guesses

Once a visually good match is found:

  1. Switch to a fitting method such as lmfit, odr, or emcee
  2. The last slider values are retained as the initial guesses
  3. Click Fit to run the optimization from that point

This can significantly improve convergence and avoid local minima.

Why use manual mode?

  • Quickly verify that the formula is well-formed
  • Understand parameter roles and interactions
  • Pre-tune parameters for faster and more accurate fitting
  • Compare models before choosing one