MATLAB: How to plot point x on a line

plot

i am new in matlab i want to highlight point intersection point on a line in graph i can plot a point but not able to plot the point on line my code is here:

   function[ x y]= test (x1,y1,x2,y2)
y=((-x1)+y1*(y2-y1))/(x2-x1);
x=((-y1*(x1-x2))/(y1-y2))+x1;
plot(x,y,'ro')
  end

Best Answer

I agree that the question is a bit unclear.

If you're wondering how to find and highlight the intersection point(s) between two curves this below code snippet might be helpful:

x1 = [1 2 3 4]; y1 = [0 2 4 6];
x2 = [1 2 3 4]; y2 = [6 4 2 0];
% find intersection
[x_intsect, y_intsect] = polyxpoly(x1, y1, x2, y2)
% plot everything on a single figure
figure;
hold on;
plot(x1, y1, 'k-', x2, y2, 'r-');
plot(x_intsect, y_intsect, 'bo');
hold off;

Related Solutions

MATLAB: How to merge multiple graphs/vectors in one!

To begin with, your data are apparently all row vectors, so I would concatenate them as cell arrays:

xall = {fliplr(x1); fliplr(x2); x3; x4; fliplr(x5); fliplr(x6); x7; x8};
yall = {fliplr(y1); fliplr(y2); y3; y4; fliplr(y5); fliplr(y6); y7; y8};
figure(1)
hold on
for k1 = 1:size(xall,1)
    plot(xall{k1}, yall{k1}, 'x')
end
hold off

I would not bother with unique, since the points will simply overplot each other, since you’re plotting them as discrete points and not as lines. In R2014b, the colours will cycle automatically. Otherwise, you will have to cycle through the colours yourself, but that is not difficult.

MATLAB: How to take a value if it goes through a straight line or another specific point

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;
x1=0;
x2=10;
y1=0;
y2=10;
wholeHousex = [x1, x2, x2, x1, x1];
wholeHousey = [y1, y1, y2, y2, y1];
plot(wholeHousex, wholeHousey, 'b-', 'LineWidth', 3);
xlabel('Length')
ylabel('Width')
hold on;
text(3,5,'total house W-L')
% Room 1
x1=0;
y1=0;
x2=2;
y2=3;
room1x = [x1, x2, x2, x1,x1];
room1y = [y1, y1, y2, y2,y1];
plot(room1x, room1y, 'r', 'LineWidth', 3);
hold on;
% Room 2
x1=2;
y1=0;
x2=5;
y2=3;
room2x = [x1, x2, x2, x1,x1];
room2y = [y1, y1, y2, y2,y1];
plot(room2x, room2y, 'g', 'LineWidth', 3);
hold on;
% Room 3
x1=5;
y1=0;
x2=10;
y2=3;
room3x = [x1, x2, x2, x1,x1];
room3y = [y1, y1, y2, y2,y1];
plot(room3x, room3y, 'k', 'LineWidth', 3);
hold on;
% Room 4
x1=0;
y1=6;
x2=3;
y2=10;
room4x = [x1, x2, x2, x1, x1];
room4y = [y1, y1, y2, y2, y1];
% Ask the user to click two lines.  You can use improfile() or imdistline() of you have the Image Processing Toolbox.
uiwait(helpdlg('Click on two points.'))
[xUser, yUser] = ginput(2) %this gives me the 2 points
plot(xUser, yUser, 'ro--', 'LineWidth', 2);
% Make flag array to find out if the point is in there.
% One row for every room.  We don't need to check if it's in the entire house since we assume it will be.
inRoom = false(3, 2); % Column 1 for point 1, column 2 for point 2.
% See if points 1 and 2 are in room 1.
if inpolygon(xUser(1), yUser(1), room1x, room1y)
	% The first point is in the whole house

	inRoom(1, 1) = true;
end
if inpolygon(xUser(2), yUser(2), room1x, room1y)
	% The first point is in the whole house
	inRoom(1, 2) = true;
end
% See if points 1 and 2 are in room 2.
if inpolygon(xUser(1), yUser(1), room2x, room2y)
	% The first point is in room 2.
	inRoom(2, 1) = true;
end
if inpolygon(xUser(2), yUser(2), room2x, room2y)
	% The second point is in room 2.
	inRoom(2, 2) = true;
end
% See if points 1 and 2 are in room 3.
if inpolygon(xUser(1), yUser(1), room3x, room3y)
	% The first point is in room 3.
	inRoom(3, 1) = true;
end
if inpolygon(xUser(2), yUser(2), room3x, room3y)
	% The second point is in room 3.
	inRoom(3, 2) = true;
end
% Display results:
inRoom
% Find out if both points are in the same room
roomCount = sum(inRoom, 2)
if any(roomCount == 2)
	% Then both points are in the same room
	message = 'Both points are in the same room';
	uiwait(helpdlg(message));
	return;
end
% Find out where point 1 is by inspecting column 1 for a 1.
point1room = find(inRoom(:, 1))
% Find out where point 2 is by inspecting column 2 for a 1.
point2room = find(inRoom(:, 2))
if isempty(point1room)
	% In whole house but not in any room.  Just say it's room 0.
	point1room = 0;
end
if isempty(point2room)
	% In whole house but not in any room.
	point2room = 0;
end
message = sprintf('Point 1 is in room %d, and Point 2 is in room %d', ...
	point1room, point2room);
uiwait(helpdlg(message));

Best Answer

Related Solutions

MATLAB: How to merge multiple graphs/vectors in one!

MATLAB: How to take a value if it goes through a straight line or another specific point

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