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

问题:

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?

回答1:

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

回答2:

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
  

回答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.

回答4:

I did it this way,

2D

% vectors I want to plot as rows (XSTART, YSTART) (XDIR, YDIR)
rays = [
  1 2   1 0 ;
  3 3   0 1 ;
  0 1   2 0 ;
  2 0   0 2 ;
] ;

% quiver plot
quiver( rays( :,1 ), rays( :,2 ), rays( :,3 ), rays( :,4 ) );

3D

% vectors I want to plot as rows (XSTART, YSTART, ZSTART) (XDIR, YDIR, ZDIR)
rays = [
  1 2 0  1 0 0;
  3 3 2  0 1 -1 ;
  0 1 -1  2 0 8;
  2 0 0  0 2 1;
] ;

% quiver plot
quiver3( rays( :,1 ), rays( :,2 ), rays( :,3 ), rays( :,4 ), rays( :,5 ), rays( :,6 ) );

Based on the quiver and quiver3 documentation

回答5:

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

回答6:

            % draw simple vector from pt a to pt b
            % wtr : with respect to
            scale=0;%for drawin  vectors with true scale
            a = [10 20 30];% wrt origine O(0,0,0)
            b = [10 10 20];% wrt origine O(0,0,0)

            starts=a;% a now is the origine of my vector to draw (from a to b) so we made a translation from point O to point  a = to vector a 
            c = b-a;% c is the new coordinates of b wrt origine a 
            ends=c;%
            plot3(a(1),a(2),a(3),'*b')
            hold on
            plot3(b(1),b(2),b(3),'*g')

             quiver3(starts(:,1), starts(:,2), starts(:,3), ends(:,1), ends(:,2), ends(:,3),scale);% Use scale = 0 to plot the vectors without the automatic scaling.
            % axis equal
            hold off