Draw vertical line in seaborn pairplot [duplicate] - python-3.x

Question

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How to add individual vlines to every subplot of seaborn FacetGrid
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Closed 1 year ago.
I have the following plot code in seaborn
import seaborn as sns
import matplotlib.pyplot as plt
iris= sns.load_dataset("iris")
g= sns.pairplot(iris,
x_vars=["sepal_width", "sepal_length"],
y_vars=["petal_width"])
This produces the following output
Now I am trying to add a vertical line at x=3 on both plots
I have tried using plt.axvline(x=3, ls='--', linewidth=3, color='red') however that draws the line only on the last plot, as shown below
How can I have the vertical line drawn on both plots?
I have tried g.map_offdiag(plt.axvline(x=1, ls='--', linewidth=3, color='red')) and the g.map() variant, however I get the following error.
TypeError Traceback (most recent call last)
<ipython-input-12-612fcf2a7fef> in <module>
9
10 # plt.axvline(x=3, ls='--', linewidth=3, color='red')
---> 11 g.map_offdiag(plt.axvline(x=1, ls='--', linewidth=3, color='red'))
12
13
~/PycharmProjects/venv/lib/python3.8/site-packages/seaborn/axisgrid.py in map_offdiag(self, func, **kwargs)
1318 if x_var != y_var:
1319 indices.append((i, j))
-> 1320 self._map_bivariate(func, indices, **kwargs)
1321 return self
1322
~/PycharmProjects/venv/lib/python3.8/site-packages/seaborn/axisgrid.py in _map_bivariate(self, func, indices, **kwargs)
1463 if ax is None: # i.e. we are in corner mode
1464 continue
-> 1465 self._plot_bivariate(x_var, y_var, ax, func, **kws)
1466 self._add_axis_labels()
1467
~/PycharmProjects/venv/lib/python3.8/site-packages/seaborn/axisgrid.py in _plot_bivariate(self, x_var, y_var, ax, func, **kwargs)
1471 def _plot_bivariate(self, x_var, y_var, ax, func, **kwargs):
1472 """Draw a bivariate plot on the specified axes."""
-> 1473 if "hue" not in signature(func).parameters:
1474 self._plot_bivariate_iter_hue(x_var, y_var, ax, func, **kwargs)
1475 return
/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/inspect.py in signature(obj, follow_wrapped)
3091 def signature(obj, *, follow_wrapped=True):
3092 """Get a signature object for the passed callable."""
-> 3093 return Signature.from_callable(obj, follow_wrapped=follow_wrapped)
3094
3095
/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/inspect.py in from_callable(cls, obj, follow_wrapped)
2840 def from_callable(cls, obj, *, follow_wrapped=True):
2841 """Constructs Signature for the given callable object."""
-> 2842 return _signature_from_callable(obj, sigcls=cls,
2843 follow_wrapper_chains=follow_wrapped)
2844
/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/inspect.py in _signature_from_callable(obj, follow_wrapper_chains, skip_bound_arg, sigcls)
2214
2215 if not callable(obj):
-> 2216 raise TypeError('{!r} is not a callable object'.format(obj))
2217
2218 if isinstance(obj, types.MethodType):
TypeError: <matplotlib.lines.Line2D object at 0x1287cc580> is not a callable object
Any suggestions?

Answer 1

The easiest way is to loop through the axes and call axvline() on each of them. Note that .ravel() converts the 2D array of axes to a 1D array.
import seaborn as sns
import matplotlib.pyplot as plt
iris = sns.load_dataset("iris")
g = sns.pairplot(iris,
x_vars=["sepal_width", "sepal_length"],
y_vars=["petal_width"])
for ax in g.axes.ravel():
ax.axvline(x=3, ls='--', linewidth=3, c='red')
plt.show()
To use g.map() or its variants, the first parameter needs to be a function (without calling), followed by the parameters. So, in theory it would be g.map(plt.axvline, x=1, ls='--', linewidth=3, color='red'). But for a pairplot, the mapped function gets called with an x and y parameter from the pairplot, which conflict with the x as parameter for axvline.