Random points between lines
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utsav kakkad
il 3 Mar 2019
Commentato: utsav kakkad
il 12 Mar 2019
Can anyone tell me how can I go about plotting random points between two straight lines?
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Image Analyst
il 3 Mar 2019
Try this, adapting as needed for your particular equations of lines:
% Create x axis:
x = linspace(-10, 10, 1000);
% Create line 1
m1 = 0.13;
b1 = 0.5;
y1 = m1 .* x + b1;
plot(x, y1, 'b-', 'LineWIdth', 2);
grid on;
% Create line 2
m2 = 0.5;
b2 = 1;
y2 = m2 .* x + b2;
hold on;
plot(x, y2, 'b-', 'LineWIdth', 2);
grid on;
% Get random points along x axis.
numRandomPoints = 100;
randomXValues = min(x) + (max(x)-min(x)) * rand(1, numRandomPoints);
% Get y1 and y2 at those x values
y1r = interp1(x, y1, randomXValues);
y2r = interp1(x, y2, randomXValues);
% Construct random y values for each random x value.
upperValues = max([y1r; y2r], [], 1); % Upper boundary in y direction.
lowerValues = min([y1r; y2r], [], 1); % Lower boundary in y direction.
yr = lowerValues + (upperValues - lowerValues) .* rand(1, numRandomPoints);
% All done! Now just simply plot the random points.
plot(randomXValues, yr, 'r.', 'MarkerSize', 12);
xlabel('x', 'FontSize', 15);
ylabel('y', 'FontSize', 15);
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Più risposte (5)
utsav kakkad
il 4 Mar 2019
1 Commento
Image Analyst
il 4 Mar 2019
Set b = 0, then have the slopes m be arctand(0), arctand(15), arctand(30), arctan(45), arctan(60), arctand(75), and then you'll have to handle the 90 degree situation specially. Not hard - you're a smart engineer so I'm sure you can handle it.
utsav kakkad
il 10 Mar 2019
Modificato: utsav kakkad
il 10 Mar 2019
1 Commento
Image Analyst
il 10 Mar 2019
Not sure what form you're looking for but this just looks like uniformly distributed points with lines drawn through them every 15 degrees. So you can make data like this
x = rand(1, 58);
y = rand(1, 58);
Then you can make 7 lines knowing the slopes of the lines
angles = [0, 15, 30, 45, 60, 75, 90]
slopes = atand(angles);
What more do you want, if anything?
Image Analyst
il 10 Mar 2019
Try this:
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;
fontSize = 20;
numPointsPerSector = 125;
numTrialPoints = numPointsPerSector * 6 * 10000; % Way more than enough.
% Define box
xMax = 10;
yMax = 10;
x = xMax * rand(1, numTrialPoints);
y = yMax * rand(1, numTrialPoints);
% Get angles for each point
angles = atan2d(y, x);
sectorAngleBoundaries = [0, 15, 30, 45, 60, 75, 90];
for k = 2 : length(sectorAngleBoundaries)
% Get acceptable indexes
mask = find(angles >= sectorAngleBoundaries(k-1) & angles <= sectorAngleBoundaries(k) & ...
x < xMax & y < yMax);
% Extract the prescribed number out of the masked array.
okIndexes = mask(1:numPointsPerSector);
% Store x and y into array.
thisX = x(okIndexes(1:numPointsPerSector));
thisY = y(okIndexes(1:numPointsPerSector));
plot(thisX, thisY, '.', 'MarkerSize', 13);
hold on;
% Draw lines
xLine1 = 2 * xMax * cosd(sectorAngleBoundaries(k-1));
xLine2 = 2 * xMax * cosd(sectorAngleBoundaries(k));
yLine1 = 2 * yMax * sind(sectorAngleBoundaries(k-1));
yLine2 = 2 * yMax * sind(sectorAngleBoundaries(k));
line([0, xLine1], [0, yLine1], 'Color', 'k');
line([0, xLine2], [0, yLine2], 'Color', 'k');
end
grid on;
xlim([0, xMax]);
ylim([0, yMax]);
xlabel('X', 'FontSize', fontSize);
ylabel('Y', 'FontSize', fontSize);
caption = sprintf('%d points per sector', numPointsPerSector);
title(caption, 'FontSize', fontSize);
axis square;
Probably a better way is to adapt the code in the FAQ: https://matlab.fandom.com/wiki/FAQ#How_do_I_create_a_set_of_random_locations_within_a_circle.3F
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