How do you draw a line between two points in python?

To create line segments between two points in matplotlib, we can take the following steps

• Set the figure size and adjust the padding between and around the subplots.
• To make two points, create two lists.
• Extract x and y values from point1 and point2.
• Plot x and y values using plot[] method.
• Place text for both the points.
• To display the figure, use show[] method.

Example

import matplotlib.pyplot as plt
plt.rcParams["figure.figsize"] = [7.50, 3.50]
plt.rcParams["figure.autolayout"] = True
point1 = [1, 2]
point2 = [3, 4]
x_values = [point1[0], point2[0]]
y_values = [point1[1], point2[1]]
plt.plot[x_values, y_values, 'bo', linestyle="--"]
plt.text[point1[0]-0.015, point1[1]+0.25, "Point1"]
plt.text[point2[0]-0.050, point2[1]-0.25, "Point2"]
plt.show[]

Output

Updated on 02-Jun-2021 08:39:05

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I know there is another very similar question, but I could not extract the information I need from it.

plotting lines in pairs

I have 4 points in the [x,y] plane: x=[x1,x2,x3,x4] and y=[y1,y2,y3,y4]

x=[-1 ,0.5 ,1,-0.5]
y=[ 0.5,  1, -0.5, -1]

Now, I can plot the four points by doing:

import matplotlib.pyplot as plt

plt.plot[x,y, 'ro']
plt.axis['equal']
plt.show[]

But, apart from the four points, I would like to have 2 lines:

1] one connecting [x1,y1] with [x2,y2] and 2] the second one connecting [x3,y3] with [x4,y4].

This is a simple toy example. In the real case I have 2N points in the plane.

How can I get the desired output: for points with two connecting lines ?

Thank you.

8-Bit Borges

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asked Feb 12, 2016 at 13:08

I think you're going to need separate lines for each segment:

import numpy as np
import matplotlib.pyplot as plt

x, y = np.random.random[size=[2,10]]

for i in range[0, len[x], 2]:
    plt.plot[x[i:i+2], y[i:i+2], 'ro-']

plt.show[]

[The numpy import is just to set up some random 2x10 sample data]

answered Feb 12, 2016 at 13:23

xnxxnx

23.5k9 gold badges65 silver badges104 bronze badges

2

You can just pass a list of the two points you want to connect to plt.plot. To make this easily expandable to as many points as you want, you could define a function like so.

import matplotlib.pyplot as plt

x=[-1 ,0.5 ,1,-0.5]
y=[ 0.5,  1, -0.5, -1]

plt.plot[x,y, 'ro']

def connectpoints[x,y,p1,p2]:
    x1, x2 = x[p1], x[p2]
    y1, y2 = y[p1], y[p2]
    plt.plot[[x1,x2],[y1,y2],'k-']

connectpoints[x,y,0,1]
connectpoints[x,y,2,3]

plt.axis['equal']
plt.show[]

Note, that function is a general function that can connect any two points in your list together.

To expand this to 2N points, assuming you always connect point i to point i+1, we can just put it in a for loop:

import numpy as np
for i in np.arange[0,len[x],2]:
    connectpoints[x,y,i,i+1]

In that case of always connecting point i to point i+1, you could simply do:

for i in np.arange[0,len[x],2]:
    plt.plot[x[i:i+2],y[i:i+2],'k-']

answered Feb 12, 2016 at 13:21

tmdavisontmdavison

59.8k12 gold badges167 silver badges150 bronze badges

1

I realize this question was asked and answered a long time ago, but the answers don't give what I feel is the simplest solution. It's almost always a good idea to avoid loops whenever possible, and matplotlib's plot is capable of plotting multiple lines with one command. If x and y are arrays, then plot draws one line for every column.

In your case, you can do the following:

x=np.array[[-1 ,0.5 ,1,-0.5]]
xx = np.vstack[[x[[0,2]],x[[1,3]]]]
y=np.array[[ 0.5,  1, -0.5, -1]]
yy = np.vstack[[y[[0,2]],y[[1,3]]]]
plt.plot[xx,yy, '-o']

Have a long list of x's and y's, and want to connect adjacent pairs?

xx = np.vstack[[x[0::2],x[1::2]]]
yy = np.vstack[[y[0::2],y[1::2]]]

Want a specified [different] color for the dots and the lines?

plt.plot[xx,yy, '-ok', mfc='C1', mec='C1']

answered May 28, 2020 at 20:49

JinjerJohnJinjerJohn

3432 silver badges5 bronze badges

1

Use the matplotlib.arrow[] function and set the parameters head_length and head_width to zero to don't get an "arrow-end". The connections between the different points can be simply calculated using vector addition with: A = [1,2], B=[3,4] --> Connection between A and B is B-A = [2,2]. Drawing this vector starting at the tip of A ends at the tip of B.

import numpy as np
import matplotlib.pyplot as plt
from matplotlib import style
style.use['fivethirtyeight']


A = np.array[[[10,8],[1,2],[7,5],[3,5],[7,6],[8,7],[9,9],[4,5],[6,5],[6,8]]]


fig = plt.figure[figsize=[10,10]]
ax0 = fig.add_subplot[212]

ax0.scatter[A[:,0],A[:,1]]


ax0.arrow[A[0][0],A[0][1],A[1][0]-A[0][0],A[1][1]-A[0][1],width=0.02,color='red',head_length=0.0,head_width=0.0]
ax0.arrow[A[2][0],A[2][1],A[9][0]-A[2][0],A[9][1]-A[2][1],width=0.02,color='red',head_length=0.0,head_width=0.0]
ax0.arrow[A[4][0],A[4][1],A[6][0]-A[4][0],A[6][1]-A[4][1],width=0.02,color='red',head_length=0.0,head_width=0.0]


plt.show[]

answered May 24, 2018 at 12:55

2Obe2Obe

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With the code below you can create multiple lines by connecting points thanks to their coordinates :

import matplotlib.pyplot as plt

# 1st line
point_1 = [1,3]
point_2 = [2,6]

# 2nd line
point_3 = [4,6]
point_4 = [1,2]

x_values = [[point_1[0], point_3[0]],[point_2[0], point_4[0]]]
y_values = [[point_1[1], point_3[1]],[point_2[1], point_4[1]]]

plt.plot[x_values, y_values, 'red']
plt.show[]

Result

answered Jan 30 at 0:02

Julien JmJulien Jm

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I would prefer LineCollection in matplotlib. See following minimum code:

import matplotlib.pyplot as plt
from matplotlib.collections import LineCollection

x = np.arange[100]
# Here are many sets of y to plot vs. x
ys = x[:50, np.newaxis] + x[np.newaxis, :]

segs = np.zeros[[50, 100, 2]]
segs[:, :, 1] = ys
segs[:, :, 0] = x

# We need to set the plot limits.
fig, ax = plt.subplots[1, 1, figsize=[7.2, 7.2]]
ax.set_xlim[x.min[], x.max[]]
ax.set_ylim[ys.min[], ys.max[]]

line_segments = LineCollection[segs]
ax.add_collection[line_segments]

A more detailed example can be found here.

answered Sep 11, 2021 at 1:48

JiadongJiadong

1,46413 silver badges32 bronze badges

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