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?
采纳的回答
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
5 个评论
Emmanuel
2014-5-29
Tunhe Zhou
2017-4-19
n = B(2)*m - A(2); This seems to be n = B(2) - A(2)*m;
Goku
2017-8-29
Thank you. But How can this be done in 3D ?
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
2020-11-27
excuse me, why do you use "vertival shift from [0,0]" . What's that ?
更多回答（1 个）
Mahesh
2014-5-29
1 个投票
A = (x1,y1); B = (x2,y2);
plot(A,B)
4 个评论
Mahesh
2014-5-29
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
2014-5-29
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
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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