Gallery examples fail with pandas >=2.1 due to invalid frequency 'ME'

[aman-coder03]

When building the documentation with pandas 2.1.4, 2 gallery examples in the irradiance-transposition section fail during execution plot_transposition_gain.py and plot_seasonal_tilt.py

Both examples use:
.resample("ME") which raises ValueError: Invalid frequency: ME

Example

import pandas as pd
import numpy as np

idx = pd.date_range("2020-01-01", periods=100, freq="H")
s = pd.Series(np.random.rand(100), index=idx)
s.resample("ME").sum()

on pandas 2.1.4 this results in ValueError: Invalid frequency: ME

It appears that "ME" is no longer recognized as a valid frequency alias in recent pandas versions
Happy to open a PR, if this change is appropriate.

[echedey-ls]

Anything greater than pandas>=2.2 should make it work.

• Broken examples due to pandas v3.0.0 #2664
• pandas-dev/pandas@a98be06#diff-adc37e76bdadb27ee30bbc55ca3537e54956062ddac142a216a16aefd59ec2f0

I doubt about what action to take.

[aman-coder03]

since Mprovides the same month-end behavior and works consistently across pandas versions (including 2.1.x), it might be safer to switch to M in these examples for broader compatibility

[cwhanse]

@aman-coder03 frequency M is deprecated since 2.1 and is removed in 3.0. I don't agree that pvlib should go backwards here.

@pvlib/pvlib-core does pvlib promise that docs will build in the minimum version requirements, e.g., pandas=1.3.3?

[wholmgren]

does pvlib promise that docs will build in the minimum version requirements, e.g., pandas=1.3.3?

No.

[cwhanse]

@aman-coder03 we'll live with this doc build error.

[aman-coder03]

i will keep this in mind when working on future doc examples