Python/maths/numerical_integration.py
Tianyi Zheng ae0fc85401
Fix ruff errors (#8936)
* Fix ruff errors

Renamed neural_network/input_data.py to neural_network/input_data.py_tf
because it should be left out of the directory for the following
reasons:

1. Its sole purpose is to be used by neural_network/gan.py_tf, which is
   itself left out of the directory because of issues with TensorFlow.

2. It was taken directly from TensorFlow's codebase and is actually
   already deprecated. If/when neural_network/gan.py_tf is eventually
   re-added back to the directory, its implementation should be changed
   to not use neural_network/input_data.py anyway.

* updating DIRECTORY.md

* Change input_data.py_tf file extension

Change input_data.py_tf file extension because algorithms-keeper bot is being picky about it

---------

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
2023-08-09 13:25:30 +05:30

66 lines
1.6 KiB
Python

"""
Approximates the area under the curve using the trapezoidal rule
"""
from __future__ import annotations
from collections.abc import Callable
def trapezoidal_area(
fnc: Callable[[float], float],
x_start: float,
x_end: float,
steps: int = 100,
) -> float:
"""
Treats curve as a collection of linear lines and sums the area of the
trapezium shape they form
:param fnc: a function which defines a curve
:param x_start: left end point to indicate the start of line segment
:param x_end: right end point to indicate end of line segment
:param steps: an accuracy gauge; more steps increases the accuracy
:return: a float representing the length of the curve
>>> def f(x):
... return 5
>>> '%.3f' % trapezoidal_area(f, 12.0, 14.0, 1000)
'10.000'
>>> def f(x):
... return 9*x**2
>>> '%.4f' % trapezoidal_area(f, -4.0, 0, 10000)
'192.0000'
>>> '%.4f' % trapezoidal_area(f, -4.0, 4.0, 10000)
'384.0000'
"""
x1 = x_start
fx1 = fnc(x_start)
area = 0.0
for _ in range(steps):
# Approximates small segments of curve as linear and solve
# for trapezoidal area
x2 = (x_end - x_start) / steps + x1
fx2 = fnc(x2)
area += abs(fx2 + fx1) * (x2 - x1) / 2
# Increment step
x1 = x2
fx1 = fx2
return area
if __name__ == "__main__":
def f(x):
return x**3
print("f(x) = x^3")
print("The area between the curve, x = -10, x = 10 and the x axis is:")
i = 10
while i <= 100000:
area = trapezoidal_area(f, -5, 5, i)
print(f"with {i} steps: {area}")
i *= 10