How to draw vectors (physical 2D/3D vectors) in MATLAB?

Question

I want to know the simplest way to plot vectors in MATLAB. For example:

a = [2 3 5];
b = [1 1 0];
c = a + b;

I want to visualize this vector addition as head-to-tail/parallelogram method. How do I plot these vectors with an arrow-head?

Answer 1

I'm not sure of a way to do this in 3D, but in 2D you can use the compass command.

Answer 2

a = [2 3 5];
b = [1 1 0];
c = a+b;

starts = zeros(3,3);
ends = [a;b;c];

quiver3(starts(:,1), starts(:,2), starts(:,3), ends(:,1), ends(:,2), ends(:,3))
axis equal

Answer 3

I found this arrow(start, end) function on MATLAB Central which is perfect for this purpose of drawing vectors with true magnitude and direction.

Answer 4

I agree with Aamir that the submission arrow.m from Erik Johnson on the MathWorks File Exchange is a very nice option. You can use it to illustrate the different methods of vector addition like so:

• Tip-to-tail method:

  o = [0 0 0];  %# Origin
  a = [2 3 5];  %# Vector 1
  b = [1 1 0];  %# Vector 2
  c = a+b;      %# Resultant
  arrowStarts = [o; a; o];        %# Starting points for arrows
  arrowEnds = [a; c; c];          %# Ending points for arrows
  arrow(arrowStarts,arrowEnds);   %# Plot arrows
  

• Parallelogram method:

  o = [0 0 0];  %# Origin
  a = [2 3 5];  %# Vector 1
  b = [1 1 0];  %# Vector 2
  c = a+b;      %# Resultant
  arrowStarts = [o; o; o];        %# Starting points for arrows
  arrowEnds = [a; b; c];          %# Ending points for arrows
  arrow(arrowStarts,arrowEnds);   %# Plot arrows
  hold on;
  lineX = [a(1) b(1); c(1) c(1)];  %# X data for lines
  lineY = [a(2) b(2); c(2) c(2)];  %# Y data for lines
  lineZ = [a(3) b(3); c(3) c(3)];  %# Z data for lines
  line(lineX,lineY,lineZ,'Color','k','LineStyle',':');  %# Plot lines