# Interactive Gauss/Voigt line fit¶

The IAGVFit tool allows to interactively fit a series of Gaussian or Voigt profiles to a given data set.

Once the data are on screen (see example below), a component can be added by using the middle mouse button. In particular, three points have to be specified from “left to right”: (1) the outer left points should approximately be placed where the profile reaches half height/depth; (2) the middle points should be placed at the “bottom” of the profile; and (3) the outer right point should be placed at the right-side equivalent of (1). Points (1) and (2) are used to estimate the width of the indicated profile and point (3) is used to estimate the area.

The parameter values are shown in the “Parameters” panel. The “active component” – by default indicated by a black line in the figure – is that whose parameter values are currently shown. The checkboxes preceding “free” indicate whether the associated parameter is considered free in the fit process.

Parameters can be fitted manually using the mouse wheel. Depending on the choice in the “mouse wheel” panel, the parameter under consideration is modified by multiplying with a given factor or adding/subtracting the amount specified in the aforementioned panel. The parameter affected by mouse-wheel action is determined using the outer left checkbox in the “Parameters” panel.

Using the “Set fit range” button, the range of the data to be fitted can be restricted. After clicking the button, to middle-mouse-button clicks into the figure are required to set the “left” and “right” edges of the git range.

## Example: Using the interactive fitter¶

```
from __future__ import print_function, division
from PyAstronomy import pyaGui
from PyAstronomy import funcFit as fuf
import numpy as np
# Data for the plot
x = np.linspace(5000., 5010, 200)
y = np.ones(len(x))
yerr = np.ones(len(x)) * 0.01
y += np.random.normal(0., 0.01, len(x))
gf = fuf.GaussFit1d()
gf["A"] = -0.3
gf["mu"] = 5004.
gf["sig"] = 0.2
y += gf.evaluate(x)
# Create interactive fitter
igv = pyaGui.IAGVFit(x, y, yerr=yerr, mode="gauss")
r = igv.interactiveFit()
print("Parameters of the fit: ", r[0])
print("Parameters of active component: ", r[1])
print("No. of components: ", r[2])
```