find_widths() AttributeError: No distance has not been given.

[tomriddle1234]

I'm trying to find the width information on filaments, other methods were ok, but no matter what, find_widths() gives error.

# there is a skeleton length reading package
from fil_finder import FilFinder2D
import astropy.units as u

fil = FilFinder2D(processed, distance=250 * u.pc, mask=skeleton)

fil.medskel(verbose=False)
fil.analyze_skeletons(branch_thresh=0* u.pix, skel_thresh=0 * u.pix, prune_criteria='length')
f = fil.filaments[0]
plt.imshow(f.skeleton(pad_size=10))
fil.exec_rht()
fil.find_widths(max_dist=0.2 * u.pc)

AttributeError                            Traceback (most recent call last)
~\AppData\Local\Temp/ipykernel_34180/1915991156.py in <module>
      5 #f.plot_radial_profile(xunit=u.pc)
      6 fil.exec_rht()
----> 7 fil.find_widths(max_dist=0.2 * u.pc)

C:\ProgramData\Anaconda3\envs\cv\lib\site-packages\fil_finder\filfinder2D.py in find_widths(self, max_dist, pad_to_distance, fit_model, fitter, try_nonparam, use_longest_path, add_width_to_length, deconvolve_width, fwhm_function, chisq_max, verbose, save_png, save_name, xunit, **kwargs)
    973                 print("Filament: %s / %s" % (n + 1, self.number_of_filaments))
    974 
--> 975             fil.width_analysis(self.image, all_skeleton_array=self.skeleton,
    976                                max_dist=max_dist,
    977                                pad_to_distance=pad_to_distance,

C:\ProgramData\Anaconda3\envs\cv\lib\site-packages\fil_finder\filament.py in width_analysis(self, image, all_skeleton_array, max_dist, pad_to_distance, fit_model, fitter, try_nonparam, use_longest_path, add_width_to_length, deconvolve_width, beamwidth, fwhm_function, chisq_max, **kwargs)
    762 
    763         # Convert quantities to pixel units.
--> 764         max_dist = self._converter.to_pixel(max_dist).value
    765         pad_to_distance = self._converter.to_pixel(pad_to_distance).value
    766 

C:\ProgramData\Anaconda3\envs\cv\lib\site-packages\fil_finder\base_conversions.py in to_pixel(self, value)
    206             return value.to(u.pix, equivalencies=self.angular_equiv)
    207         elif value.unit.is_equivalent(u.pc):
--> 208             return value.to(u.pix, equivalencies=self.physical_equiv)
    209         else:
    210             raise u.UnitConversionError("value has units of {}. It must have "

C:\ProgramData\Anaconda3\envs\cv\lib\site-packages\fil_finder\base_conversions.py in physical_equiv(self)
    186     def physical_equiv(self):
    187         if not hasattr(self, "_distance"):
--> 188             raise AttributeError("No distance has not been given.")
    189 
    190         return [(u.pix, self.distance.unit,

AttributeError: No distance has not been given.

[e-koch]

HI @tomriddle1234 -- Thanks for posting the issue! I think the problem may be that the error message is unclear. Is the input data processed an array? If it is, the issue is coming from the unit conversion path of pix -> angular -> physical units, where the angular conversion is from a FITS header that describes the image's position in the world coordinate system (https://docs.astropy.org/en/stable/io/fits/index.html). Right now there isn't a workaround to do pix -> physical unit conversion.

Just to check, do you encounter any issues when specifying the parameters only in pixel units?