MATLAB: Detect points in predefinied distnace in array

distancematrix distancepoint

Hello

I have a simple question but I can not find its solution.

I have a predefined point in an array (Xo,Yo) and I need to detect the points that lie within a distance D from (Xo,Yo). Is there any simple way to do this ?

By looking into availabe funcitons of Matlab I step upon ExhaustiveSearcher() but I think is quite complicated to use for such a simple process !

Is there any other function I am missing ?

Thank you in advance !

Best Answer

allPixels = rand(1000, 2);
point     = [0.5, 0.6];
radius    = 0.1;
% Squared Euclidean distance:
dist_2    = sum(bsxfun(@minus, allPixels, point) .^ 2, 2);
near      = dist_2 <= (radius .^ 2);

Now near is TRUE for all pixels inside the radius around the point.

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Convert to grayscale and then threshold and find the bounding box

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Try this. Adapt as needed:

% Initialization steps.
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
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% Make a circular image mask.
% Adapted from FAQ: http://matlab.wikia.com/wiki/FAQ#How_do_I_create_a_circle.3F
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% diameter, center, and image size.
% First create the image.
imageSizeX = 640;
imageSizeY = 240;
[columnsInImage, rowsInImage] = meshgrid(1:imageSizeX, 1:imageSizeY);
% Next create the circle in the image.
centerX = 320;
centerY = 120;
radius = 70;
circlePixels = (rowsInImage - centerY).^2 ...
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axis on;
title('Masked Points', 'FontSize', fontSize);

It creates an array of random points. Then it creates a circle mask. Then it erases the points that happened to fall within the circle mask.

Best Answer

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