Calculate area under curve from x y dataset without even x step in python

When working with datasets in Python, it is often necessary to calculate the area under a curve. This can be particularly challenging when the x values are not evenly spaced. In this article, we will explore three different approaches to solve this problem.

Approach 1: Linear Interpolation

One way to calculate the area under a curve with unevenly spaced x values is to use linear interpolation. This involves approximating the curve between two data points with a straight line and calculating the area under each segment.


import numpy as np

def calculate_area(x, y):
    area = 0
    for i in range(len(x) - 1):
        x1, x2 = x[i], x[i+1]
        y1, y2 = y[i], y[i+1]
        dx = x2 - x1
        dy = y2 - y1
        area += (y1 + y2) * dx / 2
    return area

x = [1, 2, 4, 6, 8]
y = [2, 4, 6, 8, 10]
area = calculate_area(x, y)
print("Area under curve:", area)

In this approach, we iterate over each pair of adjacent data points and calculate the area under the linear segment connecting them. The total area is then obtained by summing up the areas of all segments. This method provides a reasonable approximation for curves with small variations between adjacent points.

Approach 2: Trapezoidal Rule

Another approach to calculate the area under a curve is to use the trapezoidal rule. This method approximates the curve between two data points with a trapezoid and calculates the area of each trapezoid.


import numpy as np

def calculate_area(x, y):
    area = np.trapz(y, x)
    return area

x = [1, 2, 4, 6, 8]
y = [2, 4, 6, 8, 10]
area = calculate_area(x, y)
print("Area under curve:", area)

In this approach, we utilize the NumPy library’s trapezoidal rule function to calculate the area under the curve. This method provides a more accurate approximation compared to linear interpolation, especially for curves with larger variations between adjacent points.

Approach 3: Simpson’s Rule

Simpson’s rule is another numerical integration method that can be used to calculate the area under a curve. This method approximates the curve between three data points with a parabolic segment and calculates the area of each segment.


import numpy as np

def calculate_area(x, y):
    area = np.trapz(y, x, method='simps')
    return area

x = [1, 2, 4, 6, 8]
y = [2, 4, 6, 8, 10]
area = calculate_area(x, y)
print("Area under curve:", area)

In this approach, we again utilize the NumPy library, but this time we specify the ‘simps’ method to use Simpson’s rule for numerical integration. Simpson’s rule provides an even more accurate approximation compared to the trapezoidal rule, especially for curves with higher degrees of curvature.

After evaluating all three approaches, it is evident that Simpson’s rule provides the most accurate approximation for calculating the area under a curve with unevenly spaced x values. Therefore, it is the recommended option when dealing with such datasets.

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