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How can we Plot a line passing through two points?
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I am given two points (x1,y1) and (x2,y2). How can I plot a line that will pass through these two points and extend till the x and y axis?
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Accepted Answer
David Sanchez
on 29 May 2014
If you want a line connecting A and B:
A = [2 3];
B = [4 5];
plot(A,B,'*')
axis([0 10 0 10])
hold on
line(A,B)
hold off
If you want a line through A and B that extend to the plt limits:
xlim = get(gca,'XLim');
m = (B(2)-B(1))/(A(2)-A(1));
n = B(2)*m - A(2);
y1 = m*xlim(1) + n;
y2 = m*xlim(2) + n;
hold on
line([xlim(1) xlim(2)],[y1 y2])
hold off
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/175015/image.png)
5 Comments
nobody
on 11 Sep 2020
above meaning connecting the two points P1=[A(1),B(1)] and P2=[A(2),B(2)]
If you want to connect the two points C=[2,3] and D=[4,5] you do
m = (D(2)-C(2)) / (D(1)-C(1)); %slope
n = C(2) - C(1)*m %vertical shift from [0,0]
y1 = m*xlim(1) + n;
y2 = m*xlim(2) + n;
don't you?
More Answers (1)
Mahesh
on 29 May 2014
A = (x1,y1); B = (x2,y2);
plot(A,B)
4 Comments
Adam Danz
on 4 Jun 2021
Edited: Adam Danz
on 4 Jun 2021
No, this is incorrect. With the syntax plot(A,B), A contains x-values and B contains y-values. Instead, Mahesh defined A and B as (x,y) coordinates.
A simple test will show that this is incorrect,
A = [1,2];
B = [ -3,4];
plot(A,B)
hold on
plot(A(1),A(2), 'r*')
plot(B(1),B(2), 'k*')
legend('line','A','B','Location','BestOutside')
axis padded
To connect coordinates A-B you must use,
plot([A(1),B(1)], [A(2),B(2)])
Peter Hansen
on 17 Aug 2021
First of all, you need to understand that mathlab is made for matrixes and arrays, to easy big data calculation.
So all data is ussaly needed in matrix or arrays.
Therfor when ploting points, you dont plot single points like A and B but and array of x-cordinates of A and B and a array of y-cordinates of A and B.
maybe this will claryfy it for you :)
figure(2); clf(2); hold on; axis([0 10 0 10]); axis padded
% If Point A is in x=1 and y=2
% If Point B is in x=-3 and y=4
% If Point C is in x=-6 and y=-4
x_array = [1 -3 -6];
y_array = [2 4 -4];
plot(x_array(1),y_array(1),'*') % A
plot(x_array(2),y_array(2),'*') % B
plot(x_array(3),y_array(3),'*') % C
% OR to plot all points at once uncoment below line insted, and remve ",'B','C'" from legend
% plot(x_array,y_array,'*') % A, B and C
line(x_array,y_array) % line
legend('A','B','C','line','Location','BestOutside') hold off
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