# Least-Squares Circle Calculator

Analyze and calculate the best-fit circle for a set of data points using our online least-squares circle calculator. By inputting the coordinates of the data points, you can determine the center coordinates (x, y) and radius (r) of the circle that minimizes the sum of squared residuals.
Least-Squares Circle Calculator

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## What is Least-Squares Circle Calculator

A least-squares circle calculator is a tool used to find the best-fitting circle to a set of data points by minimizing the sum of squared distances between the data points and the circle. It calculates the parameters of the circle, such as the center coordinates and radius, based on the method of least squares.

The least-squares circle fitting algorithm aims to find the circle that minimizes the sum of the squared differences between the observed data points and the corresponding points on the circle. This approach is commonly used when there is noise or uncertainty in the data.

Here's how you can use a least-squares circle calculator:

1. Input your data: You need a set of 2D data points (x, y) representing the coordinates of the points in the plane.

2. Perform the calculation: The least-squares circle calculator will determine the best-fitting circle by estimating its parameters, including the x-coordinate of the center (h), the y-coordinate of the center (k), and the radius (r).

3. Interpret the results: The center coordinates (h, k) represent the location of the circle's center, and the radius (r) specifies the distance from the center to any point along the circle.

4. Visualize the circle: The calculator may provide a graphical representation of the data points and the fitted circle to help visualize the relationship.

Please note that the least-squares circle fitting algorithm assumes that the data points are distributed uniformly around the circle and that the noise or errors in the measurements are normally distributed.

If you provide me with the specific data points or any additional information, I can assist you further by performing a least-squares circle fitting analysis.

## Understanding the Best Fit Circle

In a situation in which you have the data points x, y that are distributed in a ring-shape on an x-y plane, the least-squares regression can be used to determine the equation of a circle that will best fit with the available data points; i.e., the following regression will help you to calculate the k, m, and r values of the curve:

(x âˆ’ k)2 + (y âˆ’ m)2 = r2

When you use the least-squares, you determine the "best fit" by minimizing the equation as follows:

F(k, m, r) = âˆ‘[(xi âˆ’ k)2 + (yi âˆ’ m)2 âˆ’ r2]2

The equation of the circle is linearized by the model âˆ‚F/âˆ‚k = 0, âˆ‚F/âˆ‚m = 0, and âˆ‚F/âˆ‚r = 0. As such, we have the following:

(x âˆ’ k)2 + (y âˆ’ m)2 = r2

x2 âˆ’ 2kx + k2 + y2 âˆ’ 2my + m2 = r2

x2 + y2 = 2kx + 2my + r2 âˆ’ k2 âˆ’ m2

x2 + y2 = Ax + By + C

This results in a linear equation with the coefficients A, B, and C undetermined. As such, you can use the matrices to solve the least-squares problem. Once you have determined A, B, and C, it is possible to work backward to compute k, m, and r.

## Finding A, B, and C with Matrices

The circle regression model is supported by the following matrix equation:

where n is the number of data points (xi, yi).

In a situation in which the 3-by-3 matrix outlined on the left is invertible, the A, B, and C values are unique, and this determines the best fit circle.

You can use the A, B, and C values to subsequently determine k, m, and r:

k = A/2

m = B/2

r = (âˆš4C + AÂ² + BÂ²)/2

Example:

Let's say we want to identify the equation of the circle that best fits the following four data points: (0, 1), (2, 5), (1, 6), and (7, 6).

The use of the matrix equation or the least squares circle calculator results in the following:

(x âˆ’ 4.2408)2 + (y âˆ’ 2.4630)2 = 4.32202.

## Least-Squares Circle Calculator Example

Certainly! The least-squares circle fitting method can be used to find the best-fitting circle for a given set of data points. Here's an example of how you can calculate the least-squares circle using a simple dataset:

Let's say we have the following dataset:

X = [1, 2, 3, 4, 5] # x-coordinates of data points Y = [2, 4, 6, 8, 10] # y-coordinates of data points

To calculate the least-squares circle, we need to find the center coordinates (a, b) and radius r of the circle that minimizes the sum of squared differences between the actual data points and the predicted points on the circle.

In this example, we can calculate the least-squares circle with the following steps:

Step 1: Calculate the mean of X and Y.

• Mean(X) = (1 + 2 + 3 + 4 + 5) / 5 = 3
• Mean(Y) = (2 + 4 + 6 + 8 + 10) / 5 = 6

Step 2: Calculate the deviations from the mean for X and Y.

• Deviations(X) = [1 - 3, 2 - 3, 3 - 3, 4 - 3, 5 - 3] = [-2, -1, 0, 1, 2]
• Deviations(Y) = [2 - 6, 4 - 6, 6 - 6, 8 - 6, 10 - 6] = [-4, -2, 0, 2, 4]

Step 3: Calculate the squared deviations for X and Y.

• Squared(Deviations(X)) = [(-2)^2, (-1)^2, 0^2, 1^2, 2^2] = [4, 1, 0, 1, 4]
• Squared(Deviations(Y)) = [(-4)^2, (-2)^2, 0^2, 2^2, 4^2] = [16, 4, 0, 4, 16]

Step 4: Calculate the sum of squared deviations for X and Y.

• Sum(Squared(Deviations(X))) = 4 + 1 + 0 + 1 + 4 = 10
• Sum(Squared(Deviations(Y))) = 16 + 4 + 0 + 4 + 16 = 40

Step 5: Calculate the sum of the product of X and Y deviations.

• Sum(Product(Deviations(X) * Deviations(Y))) = (-2 * -4) + (-1 * -2) + (0 * 0) + (1 * 2) + (2 * 4) = 8 + 2 + 0 + 2 + 8 = 20

Step 6: Calculate the intermediate variables A, B, and C.

• A = (Sum(Squared(Deviations(X))) + Sum(Squared(Deviations(Y)))) / N = (10 + 40) / 5 = 50 / 5 = 10
• B = (2 * Sum(Product(Deviations(X) * Deviations(Y)))) / N = (2 * 20) / 5 = 40 / 5 = 8
• C = Mean(Squared(Deviations(X))) + Mean(Squared(Deviations(Y))) = (10 / 5) + (40 / 5) = 2 + 8 = 10

Step 7: Calculate the circle center coordinates (a, b).

• a = B / (2 * C) = 8 / (2 * 10) = 0.4
• b = Mean(Y) - (a * Mean(X)) = 6 - (0.4 * 3) = 4.8

Step 8: Calculate the radius r of the circle.

• r = sqrt(A + a^2 + b^2) = sqrt(10 + 0.4^2 + 4.8^2) â‰ˆ sqrt(10 + 0.16 + 23.04) â‰ˆ sqrt(33.2) â‰ˆ 5.76

Therefore, the best-fitting circle for the given dataset has a center at (0.4, 4.8) and a radius of approximately 5.76.