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Emmanuel on 29 May 2014
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https://www.mathworks.com/matlabcentral/answers/131603-how-can-we-plot-a-line-passing-through-two-points
Commented: Peter Hansen on 17 Aug 2021
Accepted Answer: David Sanchez
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
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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
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Emmanuel on 29 May 2014
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Hey!! Thanks a lot! Now my lines are intersecting when I changed the xlim from [-10 10] from your code. But the form a triangle in the negative axis
Tunhe Zhou on 19 Apr 2017
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n = B(2)*m - A(2); This seems to be n = B(2) - A(2)*m;
Goku on 29 Aug 2017
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Thank you. But How can this be done in 3D ?
nobody on 11 Sep 2020
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https://www.mathworks.com/matlabcentral/answers/131603-how-can-we-plot-a-line-passing-through-two-points#comment_1005073
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?
Ronaldo Lim on 27 Nov 2020
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excuse me, why do you use "vertival shift from [0,0]" . What's that ?
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More Answers (1)
Mahesh on 29 May 2014
A = (x1,y1); B = (x2,y2);
plot(A,B)
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Mahesh on 29 May 2014
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Example: Want to draw the line b/w the points (5,10) and (15,30).
A = (5,15); B = (10,30); plot(A,B)
Emmanuel on 29 May 2014
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https://www.mathworks.com/matlabcentral/answers/131603-how-can-we-plot-a-line-passing-through-two-points#comment_216597
monospaced Thanks!!
Adam Danz on 4 Jun 2021
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Edited: Adam Danz on 4 Jun 2021
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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
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https://www.mathworks.com/matlabcentral/answers/131603-how-can-we-plot-a-line-passing-through-two-points#comment_1692942
Open in MATLAB Online
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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