Matplotlib - 网格和绘制颜色编码的y值/数据范围

Question

我是一名新的matplotlib用户。我想绘制一个颜色编码的数据线，或者更好的是，一个颜色编码的数据范围。在y轴上对间隔进行颜色编码。以下是一个简单的演示脚本:

import matplotlib.pyplot as plt

# dummy test data
datapoints = 25
maxtemps = [ 25, 24, 24, 25, 26, 27, 22, 21, 22, 19, 17, 14, 13, 12, 11, 12, 11, 10, 9, 9, 9, 8, 9, 9, 8 ]
mintemps = [ 21, 22, 22, 22, 23, 24, 18, 17, 16, 14, 10, 8, 8, 7, 7, 6, 5, 5, 5, 4, 4, 4, 3, 4, 3 ]
times = list(xrange(datapoints))

# cap a filled plot at a given level
def capped(indata, cap):
    outdata  = [0] * datapoints
    lcount = 0

    while lcount < datapoints:
        if indata[lcount] > cap:
            outdata[lcount] = cap
        else:
            outdata[lcount] = indata[lcount]
        lcount += 1
    return outdata

fig = plt.figure()

ax1 = fig.add_subplot(111)
ax1.fill_between(times, 0, maxtemps, color='#FF69B4', zorder=1, linewidth=0.1)
ax1.fill_between(times, 0, capped(maxtemps,25), color='#F08228', zorder=2, linewidth=0.1)
ax1.fill_between(times, 0, capped(maxtemps,20), color='#E6AF2D', zorder=3, linewidth=0.1)
ax1.fill_between(times, 0, capped(maxtemps,15), color='#E6DC32', zorder=4, linewidth=0.1)
ax1.fill_between(times, 0, capped(maxtemps,10), color='#A0E632', zorder=5, linewidth=0.1)
ax1.fill_between(times, 0, capped(maxtemps,5), color='#00DC00', zorder=6, linewidth=0.1)
ax1.fill_between(times, 0, mintemps, color='#FFFFFF', zorder=7, linewidth=0.1)
plt.setp(ax1.get_xticklabels(), visible=False)
ax1.grid(True, zorder=8)
ylim(0)
plt.draw()
plt.show()

完成了大部分工作但有两个问题。

1. 是否有一种更直接、更优雅的方法来使用matplotlib实现相同的效果？即绘制一个1D数组的时间序列数据，或者说明两组这样的数据之间的范围（例如最高，最低温度）？

2. 尽我所能，我无法让网格线绘制在图形的顶部。它们总是似乎位于第一组绘制的数据的顶部，然后被随后绘制的数据所覆盖，留下了绘图的下半部分空白。使用zorder似乎被忽略了。

非常感谢。

- Fin Son

Answer 1

回答你的第二个问题：

你可以将所有的fill_between zorder设置为0.1、0.2、0.3等等。

网格线属于x轴和y轴，x轴和y轴的zorder为2.5。因此，任何小于2.5的zorder都会显示在网格线下面。

我写了一些类似于你的代码，但使用for循环、numpy.interp和numpy.clip来进行剪辑绘图：

import pylab as pl
import numpy as np
maxtemps = [ 25, 24, 24, 25, 26, 27, 22, 21, 22, 19, 17, 14, 13, 12, 11, 12, 11, 10, 9, 9, 9, 8, 9, 9, 8 ]
mintemps = [ 21, 22, 22, 22, 23, 24, 18, 17, 16, 14, 10, 8, 8, 7, 7, 6, 5, 5, 5, 4, 4, 4, 3, 4, 3 ]
times = list(xrange(len(mintemps)))

colors = [
    (25, '#FF69B4'),
    (20, '#F08228'),
    (15, '#E6AF2D'),
    (10, '#E6DC32'),
    (5,  '#A0E632'),
    (0,  '#00DC00')
]

# change 300 to larger number if you need more accuracy.
x = np.linspace(times[0], times[-1], 300) 
maxt = np.interp(x, times, maxtemps)
mint = np.interp(x, times, mintemps)

last_level = np.inf
for level, color in colors:    
    tmp_min = np.clip(mint, level, last_level)
    tmp_max = np.clip(maxt, level, last_level)
    pl.fill_between(x, tmp_min, tmp_max, lw=0, color=color)
    last_level = level

pl.grid(True)
pl.show()

- HYRY