带有彩色箭图的Colormap

Question

我正在绘制一张地图，上面有箭头。这些箭头表示风向、平均风速(每个方向)和位置(每个方向)。

方向由箭头的方向指示。箭头的长度表示该方向的平均风速。箭头的颜色表示在这样的方向上有风的出现。

这一切都可以通过下面的脚本很好地工作：

windData = pd.read_csv(src+'.txt'), sep='\t', names=['lat', 'lon', 'wind_dir_start', 'wind_dir_end', 'total_num_data_points','num_data_points', 'avg_windspeed']).dropna()

# plot map
m = Basemap(llcrnrlon=minLon, llcrnrlat=minLat, urcrnrlon=maxLon, urcrnrlat=maxLat, resolution='i')
Left, Bottom = m(minLon, minLat)
Right, Top = m(maxLon, maxLat)

# get x y
x, y = m(windData['lon'], windData['lat'])

# angles
angleStart = -windData['wind_start']+90
angleStart[angleStart<0] = np.radians(angleStart[angleStart<0]+360.)

angleEnd = -windData['wind_end']+90
angleEnd[angleEnd<0] = np.radians(angleEnd[angleEnd<0]+360.)

angle = angleStart + math.radians(binSize/2.)

xux = np.cos(angle) * windData['avg_windspeed']
yuy = np.sin(angle) * windData['avg_windspeed']

# occurence
occurence = (windData['num_data_points']/windData['total_num_data_points'])

xi = np.linspace(minLon, maxLon, 300)
yi = np.linspace(minLat, maxLat, 300)

# plotting
## xux and yuy are used negatively because they are measured as "coming from" and displayed as "going to"
# To make things more readable I left a threshold for the occurence out
# I usually plot x, y, xux, yuy and the colors as var[occurence>threshold]
Q = m.quiver(x, y, -xux, -yuy, scale=75, zorder=6, color=cm.jet, width=0.0003*Width, cmap=cm.jet)
qk = plt.quiverkey(Q, 0.5, 0.92, 3, r'$3 \frac{m}{s}$', labelpos='S', fontproperties={'weight': 'bold'})
m.scatter(x, y, c='k', s=20*np.ones(len(x)), zorder=10, vmin=4.5, vmax=39.)

这个图很好地显示了箭头，但现在我想在图的旁边添加一个颜色映射表，以指示出现的百分比。我该怎么做呢？

Answer 1

好的

常规导入，外加import matplotlib

%matplotlib inline
import matplotlib
import matplotlib.pyplot as plt
import numpy as np

伪造要绘制的数据(MCVE的tx)

NP = 10
np.random.seed(1)
x = np.random.random(NP)
y = np.random.random(NP)
angle = 1.07+np.random.random(NP) # NE to NW
velocity = 1.50+np.random.random(NP)
o = np.random.random(NP)
occurrence = o/np.sum(o)
dx = np.cos(angle)*velocity
dy = np.sin(angle)*velocity

创建一个mappable，这样Matplotib就没有理由抱怨"RuntimeError:没有mappable可用于创建色条“。

norm = matplotlib.colors.Normalize()
norm.autoscale(occurrence)
cm = matplotlib.cm.copper

sm = matplotlib.cm.ScalarMappable(cmap=cm, norm=norm)
sm.set_array([])

并绘制数据

plt.quiver(x, y, dx, dy, color=cm(norm(o)))
plt.colorbar(sm)
plt.show()

​

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参考文献：

1. A logarithmic colorbar in matplotlib scatter plot ，
2. Drawing a colorbar aside a line plot, using Matplotlib and
3. Different colours for arrows in quiver plot.

附言:在最近(肯定是在3.+) Matplotlib发布了cm.set_array咒语不再是必要的

Answer 2

你想让色条显示不同的风速吗？如果是这样的话，在Q = m.quiver(...)和qk = ...行之间放置plt.colorbar()可能就足够了。