hillas_parameters

ctapipe.image.hillas.hillas_parameters(geom, image)

Compute Hillas parameters for a given shower image.

Implementation uses a PCA analogous to the implementation in src/main/java/fact/features/HillasParameters.java from https://github.com/fact-project/fact-tools

The image passed to this function can be in three forms:

>>> from ctapipe.image.hillas import hillas_parameters
>>> from ctapipe.image.tests.test_hillas import create_sample_image, compare_hillas
>>> geom, image, clean_mask = create_sample_image(psi='0d')
>>>
>>> # Fastest
>>> geom_selected = geom[clean_mask]
>>> image_selected = image[clean_mask]
>>> hillas_selected = hillas_parameters(geom_selected, image_selected)
>>>
>>> # Mid (1.45 times longer than fastest)
>>> image_zeros = image.copy()
>>> image_zeros[~clean_mask] = 0
>>> hillas_zeros = hillas_parameters(geom, image_zeros)
>>>
>>> # Slowest (1.51 times longer than fastest)
>>> image_masked = np.ma.masked_array(image, mask=~clean_mask)
>>> hillas_masked = hillas_parameters(geom, image_masked)
>>>
>>> compare_hillas(hillas_selected, hillas_zeros)
>>> compare_hillas(hillas_selected, hillas_masked)

Each method gives the same result, but vary in efficiency

Parameters

geom: ctapipe.instrument.CameraGeometry

Camera geometry

imagearray_like

Charge in each pixel

Returns

HillasParametersContainer:

container of hillas parametesr