# IQCalc

class ginga.util.iqcalc_astropy.IQCalc(*args, **kwargs)[source]

Bases: `IQCalc`

This is `ginga.util.iqcalc.IQCalc` that uses `astropy`.

This subclass has an extra `self.fitter` attribute for `astropy` fitting.

Methods Summary

 `calc_fwhm`(arr1d[, medv, method_name]) Calculate FWHM for the given input array. `calc_fwhm_gaussian`(arr1d[, medv]) FWHM calculation on a 1D array by using least square fitting of a Gaussian function on the data. `calc_fwhm_lorentz`(arr1d[, medv]) FWHM calculation on a 1D array by using least square fitting of a Lorentz function on the data. `calc_fwhm_moffat`(arr1d[, medv]) FWHM calculation on a 1D array by using least square fitting of a Moffat function on the data. `centroid`(data, xc, yc, radius) Calculate centroid from center of mass. `find_bright_peaks`(data[, threshold, sigma, ...]) Find bright peak candidates in in the given data. `gaussian`(x, p) Evaluate Gaussian function in 1D. `lorentz`(x, p) Evaluate Lorentz function in 1D. `moffat`(x, p) Evaluate Moffat function in 1D.

Methods Documentation

calc_fwhm(arr1d, medv=None, method_name='gaussian')[source]

Calculate FWHM for the given input array.

Parameters
arr1darray-like

1D array cut in either X or Y direction on the object.

medvfloat or `None`

Median of the data. If not given, it is calculated from `arr1d`.

method_name{‘gaussian’, ‘moffat’, ‘lorentz’}

Function to use for fitting.

Returns
res`Bunch`

Fitting results.

Raises
NotImplementedError

Given function is not supported.

calc_fwhm_gaussian(arr1d, medv=None, **kwargs)[source]

FWHM calculation on a 1D array by using least square fitting of a Gaussian function on the data.

Parameters
arr1darray-like

1D array cut in either X or Y direction on the object.

medvfloat or `None`

Median of the data. If not given, it is calculated from `arr1d`.

kwargsdict

Not used; for backward-compatible API call only.

Returns
res`Bunch`

Fitting results.

Raises
IQCalcError

Fitting failed.

calc_fwhm_lorentz(arr1d, medv=None, **kwargs)[source]

FWHM calculation on a 1D array by using least square fitting of a Lorentz function on the data.

Parameters
arr1darray-like

1D array cut in either X or Y direction on the object.

medvfloat or `None`

Median of the data. If not given, it is calculated from `arr1d`.

kwargsdict

Not used; for backward-compatible API call only.

Returns
res`Bunch`

Fitting results.

Raises
IQCalcError

Fitting failed.

calc_fwhm_moffat(arr1d, medv=None, **kwargs)[source]

FWHM calculation on a 1D array by using least square fitting of a Moffat function on the data.

Parameters
arr1darray-like

1D array cut in either X or Y direction on the object.

medvfloat or `None`

Median of the data. If not given, it is calculated from `arr1d`.

kwargsdict

Not used; for backward-compatible API call only.

Returns
res`Bunch`

Fitting results.

Raises
IQCalcError

Fitting failed.

Calculate centroid from center of mass.

Parameters
dataarray-like

Data array.

xc, ycint

X and Y indices of the approximate center.

Half-width of the region to consider around the given center.

Returns
x, yfloat

Centroid indices.

Raises
IQCalcError

Missing dependency.

Find bright peak candidates in in the given data.

Parameters
dataarray-like

Input data to find peaks from.

thresholdfloat or `None`

Detection threshold. Below this value, an object is not considered a candidate. If not given, a default is calculated using `get_threshold()` with the given `sigma`.

sigmafloat

Sigma for the threshold.

Pixel radius for determining local maxima. If the desired objects are larger in size, specify a larger radius.

Returns
peakslist of tuple

A list of candidate object coordinate tuples `(x, y)` in data.

gaussian(x, p)[source]

Evaluate Gaussian function in 1D.

Parameters
xarray-like

X values.

ptuple of float

Parameters for Gaussian, i.e., `(mean, stddev, amplitude)`.

Returns
yarray-like

Y values.

lorentz(x, p)[source]

Evaluate Lorentz function in 1D.

Parameters
xarray-like

X values.

ptuple of float

Parameters for Lorentz, i.e., `(x_0, fwhm, amplitude)`.

Returns
yarray-like

Y values.

moffat(x, p)[source]

Evaluate Moffat function in 1D.

Parameters
xarray-like

X values.

ptuple of float

Parameters for Moffat, i.e., `(x_0, gamma, alpha, amplitude)`, where `x_0` a.k.a. mean and `gamma` core width.

Returns
yarray-like

Y values.