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Corrected plot_anomaly_log_colouring for new Matplotlib linscale rules. #4115

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May 4, 2021
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Corrected plot_anomaly_log_colouring for new Matplotlib linscale rules. #4115

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4 changes: 2 additions & 2 deletions docs/gallery_code/general/plot_anomaly_log_colouring.py
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Original file line number Diff line number Diff line change
Expand Up @@ -68,13 +68,13 @@ def main():
# Create a 'logarithmic' data normalization.
anom_norm = mcols.SymLogNorm(
linthresh=minimum_log_level,
linscale=1,
linscale=0.01,
vmin=-maximum_scale_level,
vmax=maximum_scale_level,
)
# Setting "linthresh=minimum_log_level" makes its non-logarithmic
# data range equal to our 'zero band'.
# Setting "linscale=1" maps the whole zero band to the middle colour value
# Setting "linscale=0.01" maps the whole zero band to the middle colour value
# (i.e., 0.5), which is the neutral point of a "diverging" style colormap.
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@rcomer rcomer May 4, 2021 •
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I'll be honest, I'm really struggling to match this comment up with what the mpl docs say about linscale. I'm getting the feeling that either the original comment was wrong, or the behaviour has changed. Or I'm just missing something... 😕

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It's the first bit about "linthresh=minimum_log_level" that I'm particularly struggling with, rather than the changed bit.

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The language of these comment lines makes no sense to me either, but I assumed that to be due to the writer's greater knowledge in this area. Seems important to understand and correct before merging.

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Looks like @pp-mo was the originator, but a Whole Seven Years Ago!!! #1040

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Given how much matplotlib would have moved on in seven years, it's entirely possible that there are better ways of achieving this outcome now anyway. So possibly we should just merge this now for the sake of fixing master, and open a new issue to revisit later?

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Having read in more detail and talked it over with @stephenworsley, I'm reasonably happy with how it's written already.

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@pp-mo pp-mo Jul 6, 2021 •
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Just found this.
FWIW there was a perfectly good documentation for this up to Matplotlib v3.3,
https://matplotlib.org/3.3.4/api/_as_gen/matplotlib.colors.SymLogNorm.html

But they seem to have lost it somewhere since ??

update : It's not unique : a lot of the classes have lost their docstring details.
I'm trying to work out how to raise this as an issue.


# Create an Axes, specifying the map projection.
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5 changes: 2 additions & 3 deletions lib/iris/tests/results/imagerepo.json
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Original file line number Diff line number Diff line change
Expand Up @@ -23,8 +23,7 @@
"gallery_tests.test_plot_anomaly_log_colouring.TestAnomalyLogColouring.test_plot_anomaly_log_colouring.0": [
"https://scitools.github.io/test-iris-imagehash/images/v4/ec4464e185a39f93931e9b1e91696d2949dde6e63e26a47a5ad391938d9a5a0c.png",
"https://scitools.github.io/test-iris-imagehash/images/v4/ecc164e78e979b19b3789b0885a564a56cc2c65e3ec69469db1bdb9a853c1e24.png",
"https://scitools.github.io/test-iris-imagehash/images/v4/ece164e68e979b19b3781b0885a564a56ccac65e3ec69469db1bdb9a853c1e24.png",
"https://scitools.github.io/test-iris-imagehash/images/v4/ece164e796979a1b39781b2881a564a56ccac6da3e87947bcb1bdb9a843c1e24.png"
"https://scitools.github.io/test-iris-imagehash/images/v4/ece164e68e979b19b3781b0885a564a56ccac65e3ec69469db1bdb9a853c1e24.png"
],
"gallery_tests.test_plot_atlantic_profiles.TestAtlanticProfiles.test_plot_atlantic_profiles.0": [
"https://scitools.github.io/test-iris-imagehash/images/v4/9f8260536bd28e1320739437b5f437b0a51d66f4cc5d08fcd00fdb1c93fcb21c.png",
Expand Down Expand Up @@ -1048,4 +1047,4 @@
"https://scitools.github.io/test-iris-imagehash/images/v4/82fe81987fdf77ffe0002addd4002805dd28df67d9a9d4625bfddc209841de20.png",
"https://scitools.github.io/test-iris-imagehash/images/v4/82fa80997f547799a0037a00d52f0956ddaf9f7e98a1816e09f5d8260bfffe00.png"
]
}
}