More cluster methods for matched filter

[zxdawn]

See this paper: https://www.sciencedirect.com/science/article/pii/S2590162126000055#sec5:~:text=Hard%20Clustering%2C%20Fuzzy%20Clustering%20and%20Spectral%20angle%20Mapper. We can add more cluster methods for matched filter.

HyperGas/hypergas/retrieve.py

Lines 107 to 120 in 09f7ab2

	if cluster:
	segmentation = PCA_kmeans(self.radiance)
	elif land_mask:
	# get lon and lat from area attrs
	lons, lats = self.radiance.attrs['area'].get_lonlats()
	# create land mask
	segmentation = Land_mask(lons, lats, land_mask_source)
	else:
	# set all pixels as the same type
	segmentation = xr.DataArray(np.ones((self.radiance.sizes['y'],
	self.radiance.sizes['x'])),
	dims=['y', 'x'],
	)
	segmentation.attrs['description'] = ''