trplot function not plotting a 4x4 matrix

i'm trying to plot NewDist

but it gives me this error

Error in trplot (line 365)

   set(hg, 'Matrix', T);

Error in Untitled3 (line 9)

   trplot(NewDist,'view',[15 15])

B = [ 0 1 0 2 ; 1 0 0 4 ; 0 0 1 -6 ; 0 0 0 1];
d = transpose([5 2 6]);
disp(d)
NewDist = transl(d) * B ;
disp(NewDist)
trplot(NewDist,'view',[15 15])

[darova]

What is trplot?

Answer 1

[Ameer Hamza]

I guess you are using trplot function from Peter Corke's robotics toolbox. Your rotation matrix

[0 1 0;
 1 0 0;
 0 0 1];

Is not a valid rotation matrix. See here: https://en.wikipedia.org/wiki/Rotation_matrix#Basic_rotations and https://math.stackexchange.com/a/1022694.

Chang your matrix B like this

B = [ 0 -1  0  2 ; 
      1  0  0  4 ; 
      0  0  1 -6 ; 
      0  0  0  1];

and it will work fine.

[Hassan Bosha]

Thank you , i get it

What if i'm given different matrices

should i change them all to this form and the output be the same ?

although it works on some versions of matlab like 2015b and i'm 2017b

[Ameer Hamza]

Instead of writing it manually, It is best to create the transformation matrix using the other functions provided by the toolbox. For example

B = transl([5 2 6])*eul2tr([pi/2 0 0]);

[Hassan Bosha]

and what if i'm doing something like this

P = transpose([2,3,4]);
Rot = [ 1 0 0 ; 0 cos(45) -sin(45) ; 0 sin(45) cos(45) ];
New_P = Rot * P;
trplot(New_P)

[Hassan Bosha]

Is there a way to plot that point ?

[Ameer Hamza]

@Hassa, it depends on what you are trying to do here. The matrix you gave is a 3x3 matrix, so It can just be used to do the rotation. It cannot translate the corrdinate frame.

"Is there a way to plot that point ?"

trplot is not used to draw a point. It just draws a coordinate frame at a specified location.

[Hassan Bosha]

how can i draw a point in 3d then ?

[Ameer Hamza]

Can you explain what you are trying to do. It seems like you don't need to use trplot at all. You can try a point in 3D using plot3() command

plot3(1,2,3, '+')

will draw a point at x=1, y=2, and z=3.

Answer 2

[George Abrahams]

I assume that you want to plot the different coordinate systems, so that you can see the effect of your rotation.

While I'm not familiar with trplot, my plotframe function on File Exchange will do something similar.

You can see a number of examples for that here.