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Asked: 2020-08-08 10:12:32 +0800 CST 2020-08-08 10:12:32 +0800 CST

Join with lines Scatter Plot Matplotlib

  • 772

I have a scatterplot like the one shown in the figure and I want to connect the points with segments, but not all, but in groups of 5. That is, four segments that join the first 5 points, four segments that join the following 5 points and so on... that's 120 points in total, so that would be 24 groups of 5.

scatterplot

This is the code that generated that chart:

plt.scatter(np.arange(1,121), mos[0:120])
plt.title('Imagen 1')
plt.ylabel('MOS')
plt.xlabel('Numero de Imagen')
plt.grid(True)
plt.tight_layout()
plt.show()

How do I add the segments?

From already thank you very much.

python

2 Answers

  1. Best Answer

    You can do the following:

    import numpy as np
import matplotlib.pyplot as plt
from matplotlib import collections  as mc

mos = np.random.rand(120)
y = np.arange(1,121)

fig, ax = plt.subplots()
plt.scatter(y, mos)

cant = 5
for i in range(0,len(mos),cant):
    lines = []
    for j in range(0,cant-1):
        p = [(y[i+j], mos[i+j]), (y[i+j+1], mos[i+j+1])]
        lines.append(p)

    lc = mc.LineCollection(lines, colors='red', linewidths=1)
    ax.add_collection(lc)


plt.title('Imagen 1')
plt.ylabel('MOS')
plt.xlabel('Numero de Imagen')
plt.grid(True)
plt.tight_layout()

plt.show()

    Keep in mind that I don't have the array mosso I simulate it with random values. What defines the segments is the following code:

    cant = 5
for i in range(0,len(mos),cant):
    lines = []
    for j in range(0,cant-1):
        p = [(y[i+j], mos[i+j]), (y[i+j+1], mos[i+j+1])]
        lines.append(p)

    lc = mc.LineCollection(lines, colors='red', linewidths=1)
    ax.add_collection(lc)

    That is, we walk mosin steps of cant = 5and then we build the 4 segment points, establishing the start and end point: p = [(y[i+j], mos[i+j]), (y[i+j+1], mos[i+j+1])]. The output would be something like this:

    enter image description here

    • 2

  2. You must draw the portions. Instead of using scatteryou can use plotto get the effect you want. A code example would be:

    # imports
import numpy as np
import matplotlib.pyplot as plt
plt.style.use("bmh") # esto es innecesario

# datos a dibujar
mos = np.random.randn(120)
x = np.arange(120)

# generación del plot
fig, ax = plt.subplots()
for i in range(0, len(mos), 5): # iteramos cada 5 valores para 'x' y 'mos'
    ax.plot(x[i:i+5], mos[i:i+5], 'k-o') # 'k-o' indica que queremos que:
                                         #  sea negro -> 'k', 
                                         # se unan con línea continua -> '-'y 
                                         # las uniones sean puntos 'gordos' -> 'o'
                                         # http://matplotlib.org/api/pyplot_api.html#matplotlib.pyplot.plot
ax.grid(True)
fig.show()

    Possible result: possible example

    • 1