astro py:docs

- Index
- Modules

### Navigation

- next »
- « previous |
- Astropy v5.2.1 »
- Models and Fitting (`astropy.modeling`) »
- Reference/API »
- Gaussian1D

# Gaussian1D

class astropy.modeling.functional_models.Gaussian1D(amplitude=1, mean=0, stddev=1, **kwargs)

  Bases: `Fittable1DModel`

  One dimensional Gaussian model.

  Parameters:
    amplitude `python:float` or `Quantity`.

      Amplitude (peak value) of the Gaussian - for a normalized profile (integrating to 1), set amplitude = 1 / (stddev * np.sqrt(2 * np.pi))

    mean `python:float` or `Quantity`.

      Mean of the Gaussian.

    stddev `python:float` or `Quantity`.

      Standard deviation of the Gaussian with FWHM = 2 * stddev * np.sqrt(2 * np.log(2)).

  Other Parameters:
    fixed `a` `python:dict`, optional

      A dictionary `{parameter_name: boolean}` of parameters to not be varied during fitting. True means the parameter is held fixed. Alternatively the `fixed` property of a parameter may be used.

    tied `python:dict`, optional

      A dictionary `{parameter_name: callable}` of parameters which are linked to some other parameter. The dictionary values are callables providing the linking relationship. Alternatively the `tied` property of a parameter may be used.

    bounds `python:dict`, optional

      A dictionary `{parameter_name: value}` of lower and upper bounds of parameters. Keys are parameter names. Values are a list or a tuple of length 2 giving the desired range for the parameter. Alternatively, the `min` and `max` properties of a parameter may be used.

    eqcons `python:list`, optional

      A list of functions of length `n` such that `eqcons[j](x0,*args) == 0.0` in a successfully optimized problem.

    ineqcons `python:list`, optional

      A list of functions of length `n` such that `ieqcons[j](x0,*args) >= 0.0` is a successfully optimized problem.

  See also

  `Gaussian2D`, `Box1D`, `Moffat1D`, `Lorentz1D`

  Notes

  Either all or none of input `x`, `mean` and `stddev` must be provided consistently with compatible units or as unitless numbers.

  Model formula:

  > \[f(x) = A e^{- \frac{\left(x - x_{0}\right)^{2}}{2 \sigma^{2}}}\]

  Examples

      >>> from astropy.modeling import models
      >>> def tie_center(model):
      ...         mean = 50 * model.stddev
      ...         return mean
      >>> tied_parameters = {'mean': tie_center}

  Specify that ‘mean’ is a tied parameter in one of two ways:

      >>> g1 = models.Gaussian1D(amplitude=10, mean=5, stddev=.3,
      ...                             tied=tied_parameters)

  or

      >>> g1 = models.Gaussian1D(amplitude=10, mean=5, stddev=.3)
      >>> g1.mean.tied
      False
      >>> g1.mean.tied = tie_center
      >>> g1.mean.tied
      <function tie_center at 0x...>

  Fixed parameters:

      >>> g1 = models.Gaussian1D(amplitude=10, mean=5, stddev=.3,
      ...                        fixed={'stddev': True})
      >>> g1.stddev.fixed
      True

  or

      >>> g1 = models.Gaussian1D(amplitude=10, mean=5, stddev=.3)
      >>> g1.stddev.fixed
      False
      >>> g1.stddev.fixed = True
      >>> g1.stddev.fixed
      True

      import numpy as np
      import matplotlib.pyplot as plt

      from astropy.modeling.models import Gaussian1D

      plt.figure()
      s1 = Gaussian1D()
      r = np.arange(-5, 5, .01)

      for factor in range(1, 4):
          s1.amplitude = factor
          plt.plot(r, s1(r), color=str(0.25 * factor), lw=2)

      plt.axis([-5, 5, -1, 4])
      plt.show()

  (png, svg, pdf)

  Attributes Summary

  `amplitude` |
  `fwhm` | Gaussian full width at half maximum.
  `input_units` | This property is used to indicate what units or sets of units the evaluate method expects, and returns a dictionary mapping inputs to units (or `None` if any units are accepted).
  `mean` |
  `param_names` | Names of the parameters that describe models of this type.
  `stddev` |

  Methods Summary

  `evaluate`(x, amplitude, mean, stddev) | Gaussian1D model function.
  `fit_deriv`(x, amplitude, mean, stddev) | Gaussian1D model function derivatives.

  Attributes Documentation

  amplitude = Parameter('amplitude', value=1.0)
  fwhm

    Gaussian full width at half maximum.

  input_units
  mean = Parameter('mean', value=0.0)
  param_names = ('amplitude', 'mean', 'stddev')

    Names of the parameters that describe models of this type.

    The parameters in this tuple are in the same order they should be passed in when initializing a model of a specific type. Some types of models, such as polynomial models, have a different number of parameters depending on some other property of the model, such as the degree.

    When defining a custom model class the value of this attribute is automatically set by the `Parameter` attributes defined in the class body.

  stddev = Parameter('stddev', value=1.0, bounds=(1.1754943508222875e-38, None))

  Methods Documentation

  static evaluate(x, amplitude, mean, stddev)

    Gaussian1D model function.

  static fit_deriv(x, amplitude, mean, stddev)

    Gaussian1D model function derivatives.