Different colors for arrows on the quiver section
I am drawing a graph of arrows and my code is using an external file like this:
import numpy as np
import matplotlib.pyplot as plt
import matplotlib as mpl
from pylab import rcParams
data=np.loadtxt(r'data.dat')
x = data[:,0]
y = data[:,1]
u = data[:,2]
v = data[:,3]
plt.quiver(x, y, u, v, angles='xy', scale_units='xy', scale=1, pivot='mid',color='g')
The data file basically looks like this:
0 0 0 1
0 1 1 0
1 0 1 0
1 1 0 1
which generates a graph that looks like
Is there a way to plot this with different colors for different directions of the arrows?
Ps: I have a lot more arrows in my datafile in a not very logical sentence like the one I'm using as an example.
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Perhaps this is the trick:
plt.quiver(x, y, u, v, np.arctan2(v, u), angles='xy', scale_units='xy', scale=1, pivot='mid',color='g')
Note that the fifth argument plt.quiver
is color.
UPD. If you want to control colors you should use colormaps . Here are some examples:
Use colormap with parameter colors
:
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.cm as cm
from matplotlib.colors import Normalize
%matplotlib inline
ph = np.linspace(0, 2*np.pi, 13)
x = np.cos(ph)
y = np.sin(ph)
u = np.cos(ph)
v = np.sin(ph)
colors = arctan2(u, v)
norm = Normalize()
norm.autoscale(colors)
# we need to normalize our colors array to match it colormap domain
# which is [0, 1]
colormap = cm.inferno
# pick your colormap here, refer to
# http://matplotlib.org/examples/color/colormaps_reference.html
# and
# http://matplotlib.org/users/colormaps.html
# for details
plt.figure(figsize=(6, 6))
plt.xlim(-2, 2)
plt.ylim(-2, 2)
plt.quiver(x, y, u, v, color=colormap(norm(colors)), angles='xy',
scale_units='xy', scale=1, pivot='mid')
You can also stick with the fifth argument, like in my first example (which works differently from colors
), and change the default colormap to control colors.
plt.rcParams['image.cmap'] = 'Paired'
plt.figure(figsize=(6, 6))
plt.xlim(-2, 2)
plt.ylim(-2, 2)
plt.quiver(x, y, u, v, np.arctan2(v, u), angles='xy', scale_units='xy', scale=1, pivot='mid')
You can also create your own color maps, see for example here .
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