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Error when using quantities when plotting errorbars #8871
Description
Bug report
Bug summary
I am plotting something that requires the use of standard error. I would like to keep all my arrays as Quantities arrays (using astropy quantities in this case). However, when giving yerr an array with dimensions, an exception is thrown.
Code for reproduction
import astropy.units as u import matplotlib.pyplot as plt import numpy as np x = np.linspace(0, 10, 10) y = np.sin(x*np.pi) yerr = np.random.rand(10) x_sec = x*u.second y_meter = y*u.meter yerr_meter = yerr*u.meter fig = plt.figure() ax = fig.add_subplot(111) ax.errorbar(x_sec, y_meter, yerr_meter) fig.show()
Actual outcome
Expected outcome
It is expected that errorbar would plot the points with errorbars using quantity arrays the same as regular arrays. When yerr is taken out, the quantities plot fine. Simply using yerr_meter.value does not work, as this throws an exception related to subtracting two different quantities (y_meter and yerr). I would rather not have to call .value on all the arguments.
This appears to be related to an issue raised in astropy:
astropy/astropy#3914
Matplotlib version
- Operating System: Windows 10, Scientific Linux 7.2
- Matplotlib Version: 2.0.2
- Python Version: 2.7.12
- Other Libraries: numpy 1.12.1, astropy 1.3.2
Activity
dstansby commented on Feb 2, 2018
This will be fixed by a combination of astropy/astropy#7037 and #10206
dstansby commented on Sep 25, 2018
Closing as fixed; this now works with Matplotlib >= 2.2, and Astropy 2.0.6 or Astropy 3.1 (not yet released)
vuillaut commented on Nov 25, 2020
Hi
Is this really solved? Or did another issue appear?
I copied the proposed code of the first issue.
astropy v4.1
matplotlib v3.1.3
Output
4.1 3.1.2 --------------------------------------------------------------------------- UnitConversionError Traceback (most recent call last) ~/opt/anaconda3/envs/py37/lib/python3.7/site-packages/astropy/units/quantity.py in to_value(self, unit, equivalencies) 726 try: --> 727 scale = self.unit._to(unit) 728 except Exception: ~/opt/anaconda3/envs/py37/lib/python3.7/site-packages/astropy/units/core.py in _to(self, other) 950 raise UnitConversionError( --> 951 f"'{self!r}' is not a scaled version of '{other!r}'") 952 UnitConversionError: 'Unit("s")' is not a scaled version of 'Unit(dimensionless)' During handling of the above exception, another exception occurred: UnitConversionError Traceback (most recent call last) ~/opt/anaconda3/envs/py37/lib/python3.7/site-packages/astropy/units/quantity.py in __float__(self) 1072 try: -> 1073 return float(self.to_value(dimensionless_unscaled)) 1074 except (UnitsError, TypeError): ~/opt/anaconda3/envs/py37/lib/python3.7/site-packages/astropy/units/quantity.py in to_value(self, unit, equivalencies) 729 # Short-cut failed; try default (maybe equivalencies help). --> 730 value = self._to_value(unit, equivalencies) 731 else: ~/opt/anaconda3/envs/py37/lib/python3.7/site-packages/astropy/units/quantity.py in _to_value(self, unit, equivalencies) 660 return self.unit.to(unit, self.view(np.ndarray), --> 661 equivalencies=equivalencies) 662 ~/opt/anaconda3/envs/py37/lib/python3.7/site-packages/astropy/units/core.py in to(self, other, value, equivalencies) 986 else: --> 987 return self._get_converter(other, equivalencies=equivalencies)(value) 988 ~/opt/anaconda3/envs/py37/lib/python3.7/site-packages/astropy/units/core.py in _get_converter(self, other, equivalencies) 917 --> 918 raise exc 919 ~/opt/anaconda3/envs/py37/lib/python3.7/site-packages/astropy/units/core.py in _get_converter(self, other, equivalencies) 903 return self._apply_equivalencies( --> 904 self, other, self._normalize_equivalencies(equivalencies)) 905 except UnitsError as exc: ~/opt/anaconda3/envs/py37/lib/python3.7/site-packages/astropy/units/core.py in _apply_equivalencies(self, unit, other, equivalencies) 887 "{} and {} are not convertible".format( --> 888 unit_str, other_str)) 889 UnitConversionError: 's' (time) and '' (dimensionless) are not convertible During handling of the above exception, another exception occurred: TypeError Traceback (most recent call last) <ipython-input-2-14fda73d0486> in <module> 18 fig = plt.figure() 19 ax = fig.add_subplot(111) ---> 20 ax.errorbar(x_sec, y_meter, yerr_meter) 21 fig.show() ~/opt/anaconda3/envs/py37/lib/python3.7/site-packages/matplotlib/__init__.py in inner(ax, data, *args, **kwargs) 1597 def inner(ax, *args, data=None, **kwargs): 1598 if data is None: -> 1599 return func(ax, *map(sanitize_sequence, args), **kwargs) 1600 1601 bound = new_sig.bind(ax, *args, **kwargs) ~/opt/anaconda3/envs/py37/lib/python3.7/site-packages/matplotlib/axes/_axes.py in errorbar(self, x, y, yerr, xerr, fmt, ecolor, elinewidth, capsize, barsabove, lolims, uplims, xlolims, xuplims, errorevery, capthick, **kwargs) 3428 xo, _ = xywhere(x, lower, noylims & everymask) 3429 lo, uo = xywhere(lower, upper, noylims & everymask) -> 3430 barcols.append(self.vlines(xo, lo, uo, **eb_lines_style)) 3431 if capsize > 0: 3432 caplines.append(mlines.Line2D(xo, lo, marker='_', ~/opt/anaconda3/envs/py37/lib/python3.7/site-packages/matplotlib/__init__.py in inner(ax, data, *args, **kwargs) 1597 def inner(ax, *args, data=None, **kwargs): 1598 if data is None: -> 1599 return func(ax, *map(sanitize_sequence, args), **kwargs) 1600 1601 bound = new_sig.bind(ax, *args, **kwargs) ~/opt/anaconda3/envs/py37/lib/python3.7/site-packages/matplotlib/axes/_axes.py in vlines(self, x, ymin, ymax, colors, linestyles, label, **kwargs) 1185 ymax = [ymax] 1186 -> 1187 x, ymin, ymax = cbook.delete_masked_points(x, ymin, ymax) 1188 1189 x = np.ravel(x) ~/opt/anaconda3/envs/py37/lib/python3.7/site-packages/matplotlib/cbook/__init__.py in delete_masked_points(*args) 1042 raise ValueError("Masked arrays must be 1-D") 1043 else: -> 1044 x = np.asarray(x) 1045 margs.append(x) 1046 masks = [] # list of masks that are True where good ~/opt/anaconda3/envs/py37/lib/python3.7/site-packages/numpy/core/_asarray.py in asarray(a, dtype, order) 81 82 """ ---> 83 return array(a, dtype, copy=False, order=order) 84 85 ~/opt/anaconda3/envs/py37/lib/python3.7/site-packages/astropy/units/quantity.py in __float__(self) 1073 return float(self.to_value(dimensionless_unscaled)) 1074 except (UnitsError, TypeError): -> 1075 raise TypeError('only dimensionless scalar quantities can be ' 1076 'converted to Python scalars') 1077 TypeError: only dimensionless scalar quantities can be converted to Python scalarsLachimax commented on May 30, 2021
I have the same error as above, running matplotlib 3.3.4 and astropy 4.2.1.
jklymak commented on May 30, 2021
Please try latest matplotlib. If this is still an issue please open a new issue. Thanks!
jklymak commented on May 30, 2021
This works fine with 3.4.2 and astropy 4.3.dev, so I don't think there is anything to do here.