How can we Plot a line passing through two points?

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Emmanuel
Emmanuel 2014-5-29
评论： Peter Hansen 2021-8-17
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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采纳的回答

David Sanchez
David Sanchez 2014-5-29
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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nobody
nobody 2020-9-11
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
Ronaldo Lim 2020-11-27
excuse me, why do you use "vertival shift from [0,0]" . What's that ?

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更多回答（1 个）

Mahesh
Mahesh 2014-5-29
A = (x1,y1); B = (x2,y2);
plot(A,B)
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Adam Danz
Adam Danz 2021-6-4
编辑：Adam Danz 2021-6-4
Ran in:
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
Peter Hansen 2021-8-17
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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