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Merge pull request #26068 from timhoffm/tick-formatter-example
Rewrite Tick formatters example
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‎galleries/examples/ticks/tick-formatters.py

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This example illustrates the usage and effect of the most common formatters.
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The tick format is configured via the function `~.Axis.set_major_formatter`
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or `~.Axis.set_minor_formatter`. It accepts:
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- a format string, which implicitly creates a `.StrMethodFormatter`.
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- a function, implicitly creates a `.FuncFormatter`.
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- an instance of a `.Formatter` subclass. The most common are
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- `.NullFormatter`: No labels on the ticks.
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- `.StrMethodFormatter`: Use string `str.format` method.
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- `.FormatStrFormatter`: Use %-style formatting.
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- `.FuncFormatter`: Define labels through a function.
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- `.FixedFormatter`: Set the label strings explicitly.
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- `.ScalarFormatter`: Default formatter for scalars: auto-pick the format string.
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- `.PercentFormatter`: Format labels as a percentage.
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See :ref:`formatters` for a complete list.
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"""
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import matplotlib.pyplot as plt
@@ -34,103 +51,55 @@ def setup(ax, title):
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fontsize=14, fontname='Monospace', color='tab:blue')
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# %%
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# Tick formatters can be set in one of two ways, either by passing a ``str``
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# or function to `~.Axis.set_major_formatter` or `~.Axis.set_minor_formatter`,
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# or by creating an instance of one of the various `~.ticker.Formatter` classes
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# and providing that to `~.Axis.set_major_formatter` or
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# `~.Axis.set_minor_formatter`.
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#
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# The first two examples directly pass a ``str`` or function.
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fig = plt.figure(figsize=(8, 8), layout='constrained')
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fig0, fig1, fig2 = fig.subfigures(3, height_ratios=[1.5, 1.5, 7.5])
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fig0, axs0 = plt.subplots(2, 1, figsize=(8, 2))
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fig0.suptitle('Simple Formatting')
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fig0.suptitle('String Formatting', fontsize=16, x=0, ha='left')
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ax0 = fig0.subplots()
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# A ``str``, using format string function syntax, can be used directly as a
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# formatter. The variable ``x`` is the tick value and the variable ``pos`` is
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# tick position. This creates a StrMethodFormatter automatically.
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setup(axs0[0], title="'{x} km'")
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axs0[0].xaxis.set_major_formatter('{x} km')
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setup(ax0, title="'{x} km'")
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ax0.xaxis.set_major_formatter('{x} km')
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# A function can also be used directly as a formatter. The function must take
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# two arguments: ``x`` for the tick value and ``pos`` for the tick position,
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# and must return a ``str``. This creates a FuncFormatter automatically.
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setup(axs0[1], title="lambda x, pos: str(x-5)")
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axs0[1].xaxis.set_major_formatter(lambda x, pos: str(x-5))
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fig0.tight_layout()
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fig1.suptitle('Function Formatting', fontsize=16, x=0, ha='left')
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ax1 = fig1.subplots()
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setup(ax1, title="def(x, pos): return str(x-5)")
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ax1.xaxis.set_major_formatter(lambda x, pos: str(x-5))
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# %%
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# The remaining examples use `.Formatter` objects.
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fig1, axs1 = plt.subplots(7, 1, figsize=(8, 6))
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fig1.suptitle('Formatter Object Formatting')
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fig2.suptitle('Formatter Object Formatting', fontsize=16, x=0, ha='left')
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axs2 = fig2.subplots(7, 1)
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# Null formatter
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setup(axs1[0], title="NullFormatter()")
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axs1[0].xaxis.set_major_formatter(ticker.NullFormatter())
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setup(axs2[0], title="NullFormatter()")
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axs2[0].xaxis.set_major_formatter(ticker.NullFormatter())
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# StrMethod formatter
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setup(axs1[1], title="StrMethodFormatter('{x:.3f}')")
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axs1[1].xaxis.set_major_formatter(ticker.StrMethodFormatter("{x:.3f}"))
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setup(axs2[1], title="StrMethodFormatter('{x:.3f}')")
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axs2[1].xaxis.set_major_formatter(ticker.StrMethodFormatter("{x:.3f}"))
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setup(axs2[2], title="FormatStrFormatter('#%d')")
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axs2[2].xaxis.set_major_formatter(ticker.FormatStrFormatter("#%d"))
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# FuncFormatter can be used as a decorator
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@ticker.FuncFormatter
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def major_formatter(x, pos):
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def fmt_two_digits(x, pos):
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return f'[{x:.2f}]'
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setup(axs1[2], title='FuncFormatter("[{:.2f}]".format)')
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axs1[2].xaxis.set_major_formatter(major_formatter)
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setup(axs2[3], title='FuncFormatter("[{:.2f}]".format)')
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axs2[3].xaxis.set_major_formatter(ticker.FuncFormatter(fmt_two_digits))
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# Fixed formatter
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setup(axs1[3], title="FixedFormatter(['A', 'B', 'C', ...])")
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setup(axs2[4], title="FixedFormatter(['A', 'B', 'C', 'D', 'E', 'F'])")
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# FixedFormatter should only be used together with FixedLocator.
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# Otherwise, one cannot be sure where the labels will end up.
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positions = [0, 1, 2, 3, 4, 5]
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labels = ['A', 'B', 'C', 'D', 'E', 'F']
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axs1[3].xaxis.set_major_locator(ticker.FixedLocator(positions))
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axs1[3].xaxis.set_major_formatter(ticker.FixedFormatter(labels))
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# Scalar formatter
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setup(axs1[4], title="ScalarFormatter()")
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axs1[4].xaxis.set_major_formatter(ticker.ScalarFormatter(useMathText=True))
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axs2[4].xaxis.set_major_locator(ticker.FixedLocator(positions))
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axs2[4].xaxis.set_major_formatter(ticker.FixedFormatter(labels))
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# FormatStr formatter
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setup(axs1[5], title="FormatStrFormatter('#%d')")
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axs1[5].xaxis.set_major_formatter(ticker.FormatStrFormatter("#%d"))
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setup(axs2[5], title="ScalarFormatter()")
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axs2[5].xaxis.set_major_formatter(ticker.ScalarFormatter(useMathText=True))
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# Percent formatter
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setup(axs1[6], title="PercentFormatter(xmax=5)")
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axs1[6].xaxis.set_major_formatter(ticker.PercentFormatter(xmax=5))
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setup(axs2[6], title="PercentFormatter(xmax=5)")
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axs2[6].xaxis.set_major_formatter(ticker.PercentFormatter(xmax=5))
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fig1.tight_layout()
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plt.show()
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# %%
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#
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# .. admonition:: References
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#
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# The use of the following functions, methods, classes and modules is shown
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# in this example:
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#
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# - `matplotlib.pyplot.subplots`
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# - `matplotlib.axes.Axes.text`
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# - `matplotlib.axis.Axis.set_major_formatter`
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# - `matplotlib.axis.Axis.set_major_locator`
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# - `matplotlib.axis.Axis.set_minor_locator`
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# - `matplotlib.axis.XAxis.set_ticks_position`
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# - `matplotlib.axis.YAxis.set_ticks_position`
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# - `matplotlib.ticker.FixedFormatter`
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# - `matplotlib.ticker.FixedLocator`
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# - `matplotlib.ticker.FormatStrFormatter`
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# - `matplotlib.ticker.FuncFormatter`
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# - `matplotlib.ticker.MultipleLocator`
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# - `matplotlib.ticker.NullFormatter`
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# - `matplotlib.ticker.NullLocator`
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# - `matplotlib.ticker.PercentFormatter`
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# - `matplotlib.ticker.ScalarFormatter`
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# - `matplotlib.ticker.StrMethodFormatter`

‎lib/matplotlib/ticker.py

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ax.xaxis.set_major_locator(MultipleLocator(5))
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ax2.xaxis.set_major_locator(MultipleLocator(5))
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.. _formatters:
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Tick formatting
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---------------
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