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Random points between lines

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utsav kakkad
utsav kakkad 2019-3-3
评论： utsav kakkad 2019-3-12
Can anyone tell me how can I go about plotting random points between two straight lines?

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Image Analyst
Image Analyst 2019-3-3
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);
0000 Screenshot.png

更多回答（5 个）

utsav kakkad
utsav kakkad 2019-3-4
Hey,
Your plot is great & kinda helps me.
I need a setup like this:
topology.JPG
How to go about it?
  1 个评论
Image Analyst
Image Analyst 2019-3-4
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.

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utsav kakkad
utsav kakkad 2019-3-7
so the intercept in the slope intercept equation is what you are refering to right?
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utsav kakkad
utsav kakkad 2019-3-7
编辑：Image Analyst 2019-3-9
that is what I was asking
%create the x axis
x=linspace(0,40,1000);
%creating line 1
m1=tand(0);
y1=m1*x;
plot(x,y1);
grid on;
%slope of the lines will be
%arctand(0),arctand(15),arctand(30),arctand(45),arctand(60),arctand(75)
%line 2
m2=tand(15);
y2=m2*x;
plot(x,y2);
grid on;
%line 3
m3=tand(30);
y3=m3*x;
plot(x,y3);
grid on;
%line 4
m4=tand(45);
y4=m4*x;
plot(x,y4);
grid on;
%line 5
m5=tand(60);
y5=m5*x;
plot(x,y5);
%line 6
m6=tand(75);
y6=m6*x;
plot(x,y6);
%generate random X axis values
numRand=25;
randXvals=min(x)+(max(x)-min(x))*rand(1,numRand);
%getting y vals at these x values
y1r=interp1(x,y1,randXvals);
y2r=interp1(x,y2,randXvals);
y3r=interp1(x,y3,randXvals);
y4r=interp1(x,y4,randXvals);
y5r=interp1(x,y5,randXvals);
y6r=interp1(x,y6,randXvals);
%constructing random y values for x values
uv1=max([y1r; y2r],[],1);%upper boundary for the first division in y axis
lv1=min([y1r; y2r],[],1);%lower boundary for the first division in y axis
%second division
uv2=max([y2r; y3r],[],1);%upper boundary in y axis
lv2=min([y2r; y3r],[],1);%lower boundary in y axis
%third division
uv3=max([y3r; y4r], [],1);%upper bound in y axis
lv3=min([y3r; y4r], [],1);%lower bound in y axis
%4th div
uv4=max([y4r; y5r], [],1);%upper bound in y axis
lv4=min([y4r; y5r], [],1);%lower bound in y axis
%constructing random y values
yr1=lv1+(uv1-lv1).*rand(1,numRand);
yr2=lv2+(uv2-lv2).*rand(1,numRand);
yr3=lv3+(uv3-lv3).*rand(1,numRand);
yr4=lv4+(uv4-lv4).*rand(1,numRand);
%plotting the WSN topology thus created
plot(numRand,yr1,'r.');
plot(numRand,yr2,'g.');
plot(numRand,yr3,'c.');
plot(numRand,yr4,'m.');
what is the error here ? can anyone of you please point it out ?
btw I haven't used .* in the equations that should be y=m.*x as matlab was giving the error message "Dot indexing is not supported for variables of this type."
Image Analyst
Image Analyst 2019-3-9
When I run your code I don't get an error - I get this plot:
0000 Screenshot.png

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utsav kakkad
utsav kakkad 2019-3-10
编辑：utsav kakkad 2019-3-10
Okay, now I am getting that as an output. However, how to make it distributed between the lines?
Now, I know that I can plot lines using the matlab line function.
However, I need to distribute the points between the lines which is not yet occuring. I need a topology like this for my wsn not what I am getting:-
  1 个评论
Image Analyst
Image Analyst 2019-3-10
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?

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utsav kakkad
utsav kakkad 2019-3-10
编辑：utsav kakkad 2019-3-10
I want to distribute points uniformly throughout this figure.
Between two lines there should be around 20 points.
Now, how do I plot points between two lines?
Image Analyst
Image Analyst 2019-3-10
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;
0000 Screenshot.png
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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