why the orientation of the frame is different ?

Hai all :),

I am Siti. I have a question here and hope anyone can explain to me why this happen :)

I am using a DH convention for forward kinematics and I used Matlab to calculate it.

here is my code

if true
  % code
  function case1 = upperlimbcase1(theta1,,alpha1,a1,d1)

    theta1rad = theta1*pi/180;
    alpha1rad = alpha1*pi/180;

    link1 = [cos(theta1rad) -sin(theta1rad)*cos(alpha1rad) sin(theta1rad)*sin(alpha1rad)  a1*cos(theta1rad);
    sin(theta1rad) cos(theta1rad)*cos(alpha1rad) -cos(theta1rad)*sin(alpha1rad) a1*sin(theta1rad);
    0 sin(alpha1rad) cos(alpha1rad) d1;
    0 0 0 1;]

end

and here is the result after rotate the frames at 90 degrees about z-axis.

if true
  % code

   link1 =

    0.0000   -1.0000         0    0.0000
    1.0000    0.0000         0    3.0634
         0         0    1.0000         0
         0         0         0    1.0000

end

I try to stimulate it using Simmechanics. However, the frame's rotation is different when I set the orientation vector to be [0 0 90] and [0 1 0; -1 0 0; 0 0 1].

May anyone here, explain why this happen. I expecting that for both cases, the orientation should be same. Is there anything that I miss?

Thank you in advance :)

Regards, Siti