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jfmejiat
Asked: 2022-07-20 10:14:40 +0800 CST 2022-07-20 10:14:40 +0800 CST

Problem plotting series of points in Python

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I am currently going back to Python to do some work and I find myself replicating the following graph:

enter image description here

The code I used is the following:

from matplotlib import pyplot as plt
import numpy as np

x1=[-0.196,-0.103,0.103]
x2=[-0.750,1.750,1.770]
x3=[-0.877,-0.701,-0.598]
x4=[-0.201,-0.098,0.250]

y1=[0.198,0.124,0.251]
y2=[-0.849,-0.552,-0.503]
y3=[-0.120,-0.446,-0.495]
y4=[0.845,0.796,0.695]

x_c=[-0.456,-0.456,-0.441,-0.393,-0.344,-0.339,-0.228,-0.157,-0.083,0.004,0.081,0.217,0.222,0.299,0.323,0.323,0.352]
y_c=[0.540,0.381,0.617,0.207,0.138,0.830,0.062,0.978,0.040,1.019,0.098,0.928,0.217,0.343,0.777,0.400,0.597]

plt.xlim(-1,2)
plt.ylim(-1,1)

plt.xticks(np.arange(-1, 2 + 1, 1), fontsize=12)
plt.yticks(np.arange(-1, 1 + 1, 1), fontsize=12)

plt.scatter(x1,y1, marker='s', edgecolor='black', color='lightblue', s=100)
plt.scatter(x2,y2, marker='o', edgecolor='black', color='purple', s=100)
plt.scatter(x3,y3, marker='^', edgecolor='black', color='red', s=100)
plt.scatter(x4,y4, marker='v', edgecolor='black', color='lightgreen', s=100)

plt.plot(x_c,y_c)

plt.legend(['CK','DCS','TT','TT+CK'], loc='upper right', edgecolor='black')

plt.xlabel('NMDS2', fontsize=12)
plt.ylabel('NMDS1', fontsize=12)

for pos in ['right', 'top']: 
    plt.gca().spines[pos].set_visible(False)
    
for axis in ['left','bottom']:
   plt.gca().spines[axis].set_linewidth(1.5)

plt.show()

plt.savefig('3.3.2.png')

When I run the code I get the following:

enter image description here

How can I make the series of points x_c,y_c so that it is as shown in the initial figure?

python-3.x

1 Answers

  1. Best Answer

    Good day,

    The easiest way to do this is to use matplotlib.patches.Ellipsesince if you want to do it by points, as in your question, you're going to have to go through the ellipse formulas and get the "x,y" points

    Example:

    from matplotlib import pyplot as plt
import numpy as np
from matplotlib.patches import Ellipse

x1=[-0.196,-0.103,0.103]
x2=[-0.750,1.750,1.770]
x3=[-0.877,-0.701,-0.598]
x4=[-0.201,-0.098,0.250]

y1=[0.198,0.124,0.251]
y2=[-0.849,-0.552,-0.503]
y3=[-0.120,-0.446,-0.495]
y4=[0.845,0.796,0.695]

plt.xlim(-1,2)
plt.ylim(-1,1)

plt.xticks(np.arange(-1, 2 + 1, 1), fontsize=12)
plt.yticks(np.arange(-1, 1 + 1, 1), fontsize=12)

plt.scatter(x1,y1, marker='s', edgecolor='black', color='lightblue', s=100)
plt.scatter(x2,y2, marker='o', edgecolor='black', color='purple', s=100)
plt.scatter(x3,y3, marker='^', edgecolor='black', color='red', s=100)
plt.scatter(x4,y4, marker='v', edgecolor='black', color='lightgreen', s=100)

#Crear elipse
ax = plt.gca()
ellipse = Ellipse(xy=(-0.05, 0.5), width=0.8, height=1.00, angle=-10, edgecolor='r', fc='None', lw=2)
ax.add_patch(ellipse)



plt.legend(['CK','DCS','TT','TT+CK'], loc='upper right', edgecolor='black')

plt.xlabel('NMDS2', fontsize=12)
plt.ylabel('NMDS1', fontsize=12)

for pos in ['right', 'top']: 
    plt.gca().spines[pos].set_visible(False)
    
for axis in ['left','bottom']:
    plt.gca().spines[axis].set_linewidth(1.5)

plt.show()

    This creates the following graph:

    Graph

    Another unused option Ellipseis to use the function plotbut you have to calculate the ellipse, a generic example:

    import numpy as np
from matplotlib import pyplot as plt
from math import pi

u=1.     #posición del centro en x
v=0.5    #posición del centro en y
a=2.     #radio en x
b=1.5    #radio en y

t = np.linspace(0, 2*pi, 100)
plt.plot( u+a*np.cos(t) , v+b*np.sin(t) )
plt.grid(color='lightgray',linestyle='--')
plt.show()

    This draws the following graph:

    Ellipse

    • 2