matplotlib / matplotlib/matplotlib

[Bug]: bad autolimit behavior with fill_between and transforms

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還沒有人認領這個 Issue。

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描述

### Bug summary

Using a fill_between artist with a custom transform to displace data along the y-axis, the autolimiting behavior does not work as I would expect: the axes use the non-transformed data extents. A normal line plot with the same transform does work as I would expect: autolimits match the transformed data.

### Code for reproduction

```python
import matplotlib.pyplot as plt
import numpy as np
from matplotlib.transforms import Transform

class TransformDemo(Transform):

def __init__(self):

super().__init__()

self.input_dims = 2
self.output_dims = 2
self.is_separable = False

def transform_non_affine(self, values):
output = np.empty_like(values)
output[:, 0] = values[:, 0]
output[:, 1] = 100 + values[:, 1] / (1 + np.abs(values[:, 0]))

return output

# Make some random data
y = np.random.randn(1000)
x = np.arange(len(y))

fig, ax = plt.subplots(ncols=2)

T = TransformDemo()

# First with plot, everything works as expected
ax[0].plot(x, y, transform=T + ax[0].transData)

# With fill_between, limits are not inferred correctly
ax[1].fill_between(x, -np.abs(y), np.abs(y), transform=T + ax[1].transData)
```

### Actual outcome

![image](https://user-images.githubusercontent.com/1190540/146374625-ccc09b7a-28c2-4903-a705-876243b1719c.png)

### Expected outcome

If I force the ylimits on the second plot via

```python
ax[1].set_ylim(ax[0].get_ylim())
```
it looks like
![image](https://user-images.githubusercontent.com/1190540/146374806-87c3dd31-e46a-4dd0-895d-fe508ae5d571.png)

which is basically how I would expect.

### Additional information

I'm not sure that the plot behavior is actually to spec here, but the disagreement between the two artists' behavior seems to me like a bug somewhere.

### Operating system

Ubuntu

### Matplotlib Version

3.5.0

### Matplotlib Backend

module://matplotlib_inline.backend_inline

### Python version

sys.version_info(major=3, minor=9, micro=7, releaselevel='final', serial=0)

### Jupyter version

3.2.5 (dev), 3.2.4 (app)

### Installation

conda

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研究方向

首先執行提供的 Python 重現程式碼,並比較 plot 與 fill_between 在都使用自訂 TransformDemo 和 ax.transData 時的 autolimit 行為。追蹤 fill_between artist 的限制計算並加入回歸測試;當經過轉換的 fill_between 資料產生與經過轉換的折線圖一致的限制時,即表示完成。

由索引模型根據 Issue 內容生成。

評估

技術堆疊
python
領域
data-visualization
Issue 類型
缺陷
難度
4/5
預估耗時
3-5 天
活躍度
停滯
描述清晰度
基本清楚
新手友好度
42/100

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