Let pygmt.info load datetime columns into a str dtype array

[weiji14]

Description of proposed changes

Fixes problem with pygmt.info not being able to handle datetime64 inputs. I.e. ValueError: could not convert string to float: '2021-01-01T12:34:56'.

However, users will still need to usepygmt.info(..., f="0T") until upstream issue at GenericMappingTools/gmt#4241 is resolved. Something like so:

import pandas as pd
import pygmt

table = pd.date_range(start="2020-01-01", periods=5).to_numpy()
output = pygmt.info(table=table, per_column=True, f="0T")
print(output)
# ['2020-01-01T00:00:00' '2020-01-05T00:00:00']

Also added two extra unit tests using numpy datetime64 types.

References:

• https://stackoverflow.com/questions/31553983/python-using-numpy-loadtxt-reading-a-csv-file-with-different-data-types-for-ea/31554777#31554777

Addresses #597 on the pygmt side using fix mentioned in #597 (comment). Assuming that GenericMappingTools/gmt#4241 is fixed in GMT 6.2.0, then issue #597 can be closed once PyGMT bumps minimum required GMT version to 6.2.0.

Reminders

• Run make format and make check to make sure the code follows the style guide.
• Add tests for new features or tests that would have caught the bug that you're fixing.
• Add new public functions/methods/classes to doc/api/index.rst.
• Write detailed docstrings for all functions/methods.
• If adding new functionality, add an example to docstrings or tutorials.

Slash Commands

You can write slash commands (/command) in the first line of a comment to perform
specific operations. Supported slash commands are:

• /format: automatically format and lint the code
• /test-gmt-dev: run full tests on the latest GMT development version

[weiji14]

Hmm, that crash on the Windows GMT dev test at https://github.com/GenericMappingTools/pygmt/runs/2025836161?check_suite_focus=true#step:15:86 at the start (before any tests got run) doesn't look nice.

[seisman]

/test-gmt-dev

Hmm, that crash on the Windows GMT dev test at GenericMappingTools/pygmt/runs/2025836161?check_suite_focus=true#step:15:86 at the start (before any tests got run) doesn't look nice.

It may be just a sporadic crash. Just re-triggered the dev tests.

Edit: Jobs at https://github.com/GenericMappingTools/pygmt/actions/runs/619017413

[weiji14]

Thanks! Windows tests have passed at https://github.com/GenericMappingTools/pygmt/runs/2026019634?check_suite_focus=true#step:15:867. Any other comment on this PR?