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92 lines
2.8 KiB
Markdown
92 lines
2.8 KiB
Markdown
# 使用“矩形”和“多边形”构建直方图
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使用路径补丁绘制矩形。 使用大量Rectangle实例的技术或使用PolyCollections的更快方法是在我们在mpl中使用moveto / lineto，closepoly等的正确路径之前实现的。 现在我们拥有它们，我们可以使用PathCollection更有效地绘制具有同质属性的常规形状对象的集合。 这个例子创建了一个直方图 - 在开始时设置顶点数组的工作量更大，但对于大量对象来说它应该更快。
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```python
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import numpy as np
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import matplotlib.pyplot as plt
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import matplotlib.patches as patches
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import matplotlib.path as path
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fig, ax = plt.subplots()
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# Fixing random state for reproducibility
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np.random.seed(19680801)
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# histogram our data with numpy
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data = np.random.randn(1000)
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n, bins = np.histogram(data, 50)
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# get the corners of the rectangles for the histogram
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left = np.array(bins[:-1])
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right = np.array(bins[1:])
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bottom = np.zeros(len(left))
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top = bottom + n
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# we need a (numrects x numsides x 2) numpy array for the path helper
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# function to build a compound path
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XY = np.array([[left, left, right, right], [bottom, top, top, bottom]]).T
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# get the Path object
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barpath = path.Path.make_compound_path_from_polys(XY)
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# make a patch out of it
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patch = patches.PathPatch(barpath)
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ax.add_patch(patch)
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# update the view limits
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ax.set_xlim(left[0], right[-1])
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ax.set_ylim(bottom.min(), top.max())
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plt.show()
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```
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应该注意的是，我们可以使用顶点和代码直接创建复合路径，而不是创建三维数组并使用[make_compound_path_from_polys](https://matplotlib.org/api/path_api.html#matplotlib.path.Path.make_compound_path_from_polys)，如下所示
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```python
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nrects = len(left)
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nverts = nrects*(1+3+1)
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verts = np.zeros((nverts, 2))
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codes = np.ones(nverts, int) * path.Path.LINETO
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codes[0::5] = path.Path.MOVETO
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codes[4::5] = path.Path.CLOSEPOLY
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verts[0::5, 0] = left
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verts[0::5, 1] = bottom
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verts[1::5, 0] = left
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verts[1::5, 1] = top
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verts[2::5, 0] = right
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verts[2::5, 1] = top
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verts[3::5, 0] = right
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verts[3::5, 1] = bottom
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barpath = path.Path(verts, codes)
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```
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## 参考
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此示例中显示了以下函数，方法，类和模块的使用：
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```python
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import matplotlib
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matplotlib.patches
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matplotlib.patches.PathPatch
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matplotlib.path
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matplotlib.path.Path
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matplotlib.path.Path.make_compound_path_from_polys
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matplotlib.axes.Axes.add_patch
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matplotlib.collections.PathCollection
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# This example shows an alternative to
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matplotlib.collections.PolyCollection
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matplotlib.axes.Axes.hist
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```
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## 下载这个示例
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- [下载python源码: histogram_path.py](https://matplotlib.org/_downloads/histogram_path.py)
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- [下载Jupyter notebook: histogram_path.ipynb](https://matplotlib.org/_downloads/histogram_path.ipynb) |