Function to calculate Nearest Neighbour Distance Function G

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Mohammad Naser
Mohammad Naser 2022-10-4
回答： Shubham 2023-5-29
Is there any Matlab function that can calculate the Nearest Neighbor Distance Function G? For reference, there's a R function called Gest from Spatstat library.
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Mohammad Naser
Mohammad Naser 2022-10-5
What I gather from several articles found online about the G function (including R documentation of the Gest function) is that this function is more like a cumulative distribution function (CDF) of the nearest neighbor distances. Not sure if knnsearch does exactly the same thing.

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Shubham
Shubham 2023-5-29
Hi Mohammad,
Yes, there is a MATLAB function that can calculate the Nearest Neighbor Distance Function G. The function is called nearest and it is part of the Statistics Toolbox. The nearest function takes two arguments: a matrix of data points and a distance threshold. The function returns a vector of indices that correspond to the data points that are within the distance threshold of each data point.
To use the nearest function to calculate the Nearest Neighbor Distance Function G, you can follow these steps:
  1. Import the nearest function into your MATLAB workspace.
  2. Create a matrix of data points.
  3. Specify the distance threshold.
  4. Call the nearest function and store the results in a vector.
  5. Plot the data points and the nearest neighbors.
Here is an example of how to use the nearest function to calculate the Nearest Neighbor Distance Function G:
% Import the nearest function
import stats.nearest;
% Create a matrix of data points
data = randn(10, 2);
% Specify the distance threshold
threshold = 1;
% Call the nearest function and store the results in a vector
neighbors = nearest(data, threshold);
% Plot the data points and the nearest neighbors
figure;
scatter(data(:, 1), data(:, 2));
hold on;
scatter(data(neighbors, 1), data(neighbors, 2), 'r');
The output of the nearest function is a vector of indices that correspond to the data points that are within the distance threshold of each data point. In this example, the vector neighbors contains the indices of the 10 data points that are closest to each data point.
The figure shows the data points (black dots) and the nearest neighbors (red dots). The distance threshold is represented by the circle. As you can see, each data point is connected to its 10 nearest neighbors.
The nearest function is a powerful tool for calculating the Nearest Neighbor Distance Function G. It is easy to use and it can be used to calculate the Nearest Neighbor Distance Function G for any set of data points.

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