Why are those lines not drawn?

I am using the following code to draw a triangle ABC and the medians AD1, BD2, CD3. A1, B1, C1 are points along each median that are 1/3 away from the angle the median starts from. I use line to draw the ABC triangle and the medians, but Matlab refuses to draw two of the medians. I did check the values by hand and they seem fine. All of the D and [ABC]1 points seem to be right were I want them.

Why aren't all three medians drawn?

A = [1; 0.8384];

B = [1; 1];

C = [0.8384; 1];

D1 = (B + C)/2;

D2 = (A + C)/2;

D3 = (A + B)/2;

A1 = A + (D1 - A)/3;

B1 = B + (D2 - B)/3;

C1 = C + (D3 - C)/3;

line(A,B);

hold on;

line(B,C);

line(C,A);

% Draws medians

line(A,D1);

line(B,D2);

line(C,D3);

plot(D1(1), D1(2), 'kx');

plot(D2(1), D2(2), 'kx');

plot(D3(1), D3(2), 'kx');

plot(A1(1), A1(2), 'kx');

plot(B1(1), B1(2), 'kx');

plot(C1(1), C1(2), 'kx');

hold off;

Picture is:

Answer 1

[Dimitar Slavchev]

OK, glorious user error, as expected.

When using line one shouldn't do:

line(A,B);

But instead put the x values in the first argument and the y values in the second. As in:

line([A(1) B(1)], [A(2) B(2)]);

Unfortunatelly my ABC triangle was drawing right with the wrong data and that threw me off.

I saw the answer in this question:

https://www.mathworks.com/matlabcentral/answers/156040-how-to-connect-two-points-with-a-line

Answer 2

[Cris LaPierre]

Check your values again.

line(A,D1); appears as expected

line(B,D2); is a single point (Both B values are the same, and both D2 values are the same, so no line)

line(C,D3); is the the same as line(A,D1), just in reverse. So it is getting plotted, but on top of an existing line.

[Dimitar Slavchev]

I was using line wrong.

I.e. I was expecting that:

line(A,B);

should write a line form A to B, which is wrong.

But instead it should be:

line([A(1) B(1)], [A(2) B(2)]);