Plotting dates with sharex=True leads to ValueError: ordinal must be = 1

Question

When doing some analysis, I stumbled upon a ValueError and I could boil it down to the following simple example which can reproduce the error I got: ``` import numpy as np import matplotlib.pyplot as plt import datetime as dt x = np.array([dt.datetime(2012, 10, 19, 10, 0, 0), dt.datetime(2012, 10, 19, 10, 0, 1), dt.datetime(2012, 10, 19, 10, 0, 2), dt.datetime(2012, 10, 19, 10, 0, 3)]) y = np.array([1, 3, 4, 2]) ``` When trying to plot this simple x and y array, I have no problems with: ``` fig, ax = plt.subplots() ax.plot(x, y) ``` or ``` fig, (ax1, ax2) = plt.subplots(nrows=2) ax1.plot(x, y) ``` but when adding `sharex=True`, I get an error: ``` fig, (ax1, ax2) = plt.subplots(nrows=2, sharex=True) ax1.plot(x, y) ``` The error message: ``` Traceback (most recent call last): File "C:\Python27\lib\site-packages\matplotlib\backend_bases.py", line 2445, in home self._update_view() File "C:\Python27\lib\site-packages\matplotlib\backend_bases.py", line 2818, in _update_view self.draw() Fil…

Accepted Answer

The error is avoided if you plot something on the second axis:

```
import matplotlib.pyplot as plt
import numpy as np
import datetime as dt

x = np.array([dt.datetime(2012, 10, 19, 10, 0, 0),
              dt.datetime(2012, 10, 19, 10, 0, 1),
              dt.datetime(2012, 10, 19, 10, 0, 2),
              dt.datetime(2012, 10, 19, 10, 0, 3)])

y = np.array([1, 3, 4, 2])

fig, (ax1, ax2) = plt.subplots(nrows = 2, sharex = True)
ax1.plot(x, y, 'b-')
ax2.plot(x, 1.0/y, 'r-')
plt.show()
```

Plotting dates with sharex=True leads to ValueError: ordinal must be >= 1

Solution

Problem