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Create Scatter Plot with smooth Line using Python

  • Last Updated : 15 Mar, 2021

A curve can be smoothened to reach a well approximated idea of the visualization. In this article, we will be plotting a scatter plot with the smooth line with the help of the SciPy library. To plot a smooth line scatter plot we use the following function:

  • scipy.interpolate.make_interp_spline() from the SciPy library computes the coefficients of interpolating B-spline. By importing, this function from the Scipy library and added the parameter, It is quite easier to get the smooth line to scatter plot.

Syntax:

 scipy.interpolate.make_interp_spline(x, y, k=3, t=None, bc_type=None, axis=0, check_finite=True)

Parameters:

  • x:-Abscissas
  • y:-Ordinates
  • k:-B-spline degree
  • t:-Knots
  • bc_type:-Boundary conditions
  • axis:-Interpolation axis
  • check_finite:-Whether to check that the input arrays contain only finite numbers

Return: a BSpline object of the degree k and with knots t.

  • np.linspace() function is imported from NumPy library used to get evenly spaced numbers over a specified interval used to draw a smooth line scatter plot.

Syntax:

 numpy.linspace(start, stop, num=50, endpoint=True, retstep=False, dtype=None, axis=0)

Parameters:

  • start:-The starting value of the sequence.
  • stop:-The end value of the sequence.
  • num:-Number of samples to generate.
  • endpoint:-If True, stop is the last sample.
  • retstep:-If True, return (samples, step), where the step is the spacing between samples.
  • dtype:-The type of the output array.
  • axis:- The axis in the result to store the samples.

Return: A array of num equally spaced samples in the closed interval

Approach

  • Import module
  • Create or load data
  • Create a scatter plot
  • Create a smoothened curve from the points of the scatter plot
  • Display plot

Let us start with a sample scatter plot.

Example: 

Python3




import numpy as np
import matplotlib.pyplot as plt
  
x = np.array([1, 2, 3, 4, 5])
  
y = np.array([4, 9, 1, 3, 5])
  
plt.scatter(x, y)
  
plt.show()

Output:

Now let’s visualize the scatter plot by joining points of the plot so that an uneven curve can appear i.e. without smoothening so that difference can be apparent.

Example:

Python3




import numpy as np
import matplotlib.pyplot as plt
  
x = np.array([1, 2, 3, 4, 5])
  
y = np.array([4, 9, 1, 3, 5])
  
plt.plot(x, y)
  
plt.show()

Output:

Now, We will be looking at the same example as above with the use of np.linspace() and scipy.interpolate.make_interp_spline() function.

Example:

Python3




import numpy as np
import matplotlib.pyplot as plt
from scipy.interpolate import make_interp_spline
  
x = np.array([1, 2, 3, 4, 5])
y = np.array([4, 9, 1, 3, 5])
  
xnew = np.linspace(x.min(), x.max(), 300)
  
gfg = make_interp_spline(x, y, k=3)
  
y_new = gfg(xnew)
  
plt.plot(xnew, y_new)
  
plt.show()

Output:


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