def discretize_model(model, x_range, y_range=None, mode='center', factor=10):
"""
Function to evaluate analytical model functions on a grid.
So far the function can only deal with pixel coordinates.
Parameters
----------
model : `~astropy.modeling.FittableModel` or callable.
Analytic model function to be discretized. Callables, which are not an
instances of `~astropy.modeling.FittableModel` are passed to
`~astropy.modeling.custom_model` and then evaluated.
x_range : tuple
x range in which the model is evaluated. The difference between the
upper an lower limit must be a whole number, so that the output array
size is well defined.
y_range : tuple, optional
y range in which the model is evaluated. The difference between the
upper an lower limit must be a whole number, so that the output array
size is well defined. Necessary only for 2D models.
mode : str, optional
One of the following modes:
* ``'center'`` (default)
Discretize model by taking the value
at the center of the bin.
* ``'linear_interp'``
Discretize model by linearly interpolating
between the values at the corners of the bin.
For 2D models interpolation is bilinear.
* ``'oversample'``
Discretize model by taking the average
on an oversampled grid.
* ``'integrate'``
Discretize model by integrating the model
over the bin using `scipy.integrate.quad`.
Very slow.
factor : float or int
Factor of oversampling. Default = 10.
Returns
-------
array : `numpy.array`
Model value array
Notes
-----
The ``oversample`` mode allows to conserve the integral on a subpixel
scale. Here is the example of a normalized Gaussian1D:
.. plot::
:include-source:
import matplotlib.pyplot as plt
import numpy as np
from astropy.modeling.models import Gaussian1D
from astropy.convolution.utils import discretize_model
gauss_1D = Gaussian1D(1 / (0.5 * np.sqrt(2 * np.pi)), 0, 0.5)
y_center = discretize_model(gauss_1D, (-2, 3), mode='center')
y_corner = discretize_model(gauss_1D, (-2, 3), mode='linear_interp')
y_oversample = discretize_model(gauss_1D, (-2, 3), mode='oversample')
plt.plot(y_center, label='center sum = {0:3f}'.format(y_center.sum()))
plt.plot(y_corner, label='linear_interp sum = {0:3f}'.format(y_corner.sum()))
plt.plot(y_oversample, label='oversample sum = {0:3f}'.format(y_oversample.sum()))
plt.xlabel('pixels')
plt.ylabel('value')
plt.legend()
plt.show()
"""
if not callable(model):
raise TypeError('Model must be callable.')
if not isinstance(model, FittableModel):
model = custom_model(model)()
ndim = model.n_inputs
if ndim > 2:
raise ValueError('discretize_model only supports 1-d and 2-d models.')
if not float(np.diff(x_range)).is_integer():
raise ValueError("The difference between the upper an lower limit of"
" 'x_range' must be a whole number.")
if y_range:
if not float(np.diff(y_range)).is_integer():
raise ValueError(
"The difference between the upper an lower limit of"
" 'y_range' must be a whole number.")
if ndim == 2 and y_range is None:
raise ValueError("y range not specified, but model is 2-d")
if ndim == 1 and y_range is not None:
raise ValueError("y range specified, but model is only 1-d.")
if mode == "center":
if ndim == 1:
return discretize_center_1D(model, x_range)
elif ndim == 2:
return discretize_center_2D(model, x_range, y_range)
elif mode == "linear_interp":
if ndim == 1:
return discretize_linear_1D(model, x_range)
if ndim == 2:
return discretize_bilinear_2D(model, x_range, y_range)
elif mode == "oversample":
if ndim == 1:
return discretize_oversample_1D(model, x_range, factor)
if ndim == 2:
return discretize_oversample_2D(model, x_range, y_range, factor)
elif mode == "integrate":
if ndim == 1:
return discretize_integrate_1D(model, x_range)
if ndim == 2:
return discretize_integrate_2D(model, x_range, y_range)
else:
raise DiscretizationError('Invalid mode.')
class Ellipsoid3D(custom_model(ellipsoid)):
@property
def bounding_box(self):
return ((self.z0 - self.c, self.z0 + self.c),
(self.y0 - self.b, self.y0 + self.b), (self.x0 - self.a,
self.x0 + self.a))
def discretize_model(model, x_range, y_range=None, mode='center', factor=10):
"""
Function to evaluate analytical model functions on a grid.
So far the function can only deal with pixel coordinates.
Parameters
----------
model : `~astropy.modeling.FittableModel` or callable.
Analytic model function to be discretized. Callables, which are not an
instances of `~astropy.modeling.FittableModel` are passed to
`~astropy.modeling.custom_model` and then evaluated.
x_range : tuple
x range in which the model is evaluated. The difference between the
upper an lower limit must be a whole number, so that the output array
size is well defined.
y_range : tuple, optional
y range in which the model is evaluated. The difference between the
upper an lower limit must be a whole number, so that the output array
size is well defined. Necessary only for 2D models.
mode : str, optional
One of the following modes:
* ``'center'`` (default)
Discretize model by taking the value
at the center of the bin.
* ``'linear_interp'``
Discretize model by linearly interpolating
between the values at the corners of the bin.
For 2D models interpolation is bilinear.
* ``'oversample'``
Discretize model by taking the average
on an oversampled grid.
* ``'integrate'``
Discretize model by integrating the model
over the bin using `scipy.integrate.quad`.
Very slow.
factor : float or int
Factor of oversampling. Default = 10.
Returns
-------
array : `numpy.array`
Model value array
Notes
-----
The ``oversample`` mode allows to conserve the integral on a subpixel
scale. Here is the example of a normalized Gaussian1D:
.. plot::
:include-source:
import matplotlib.pyplot as plt
import numpy as np
from astropy.modeling.models import Gaussian1D
from astropy.convolution.utils import discretize_model
gauss_1D = Gaussian1D(1 / (0.5 * np.sqrt(2 * np.pi)), 0, 0.5)
y_center = discretize_model(gauss_1D, (-2, 3), mode='center')
y_corner = discretize_model(gauss_1D, (-2, 3), mode='linear_interp')
y_oversample = discretize_model(gauss_1D, (-2, 3), mode='oversample')
plt.plot(y_center, label='center sum = {0:3f}'.format(y_center.sum()))
plt.plot(y_corner, label='linear_interp sum = {0:3f}'.format(y_corner.sum()))
plt.plot(y_oversample, label='oversample sum = {0:3f}'.format(y_oversample.sum()))
plt.xlabel('pixels')
plt.ylabel('value')
plt.legend()
plt.show()
"""
if not callable(model):
raise TypeError('Model must be callable.')
if not isinstance(model, FittableModel):
model = custom_model(model)()
ndim = model.n_inputs
if ndim > 2:
raise ValueError('discretize_model only supports 1-d and 2-d models.')
if not float(np.diff(x_range)).is_integer():
raise ValueError("The difference between the upper an lower limit of"
" 'x_range' must be a whole number.")
if y_range:
if not float(np.diff(y_range)).is_integer():
raise ValueError("The difference between the upper an lower limit of"
" 'y_range' must be a whole number.")
if ndim == 2 and y_range is None:
raise ValueError("y range not specified, but model is 2-d")
if ndim == 1 and y_range is not None:
raise ValueError("y range specified, but model is only 1-d.")
if mode == "center":
if ndim == 1:
return discretize_center_1D(model, x_range)
elif ndim == 2:
return discretize_center_2D(model, x_range, y_range)
elif mode == "linear_interp":
if ndim == 1:
return discretize_linear_1D(model, x_range)
if ndim == 2:
return discretize_bilinear_2D(model, x_range, y_range)
elif mode == "oversample":
if ndim == 1:
return discretize_oversample_1D(model, x_range, factor)
if ndim == 2:
return discretize_oversample_2D(model, x_range, y_range, factor)
elif mode == "integrate":
if ndim == 1:
return discretize_integrate_1D(model, x_range)
if ndim == 2:
return discretize_integrate_2D(model, x_range, y_range)
else:
raise DiscretizationError('Invalid mode.')
