How to insert two matrices into a matrix?

I would like to insert my matrices: R, R' and t,t' into an identity 4x4 matrix.

Then I would like to multiple them and as a result store from the final 4x4 matrix just the R^(3x3) and t^(3x1) matrices.

Thank you in advance for your help!

Answer 1

[KSSV]

I = eye(4) ;
R = rand(3) ;
t = rand(3,1) ;

I(1:3,1:3) = R ;
I(1:3,4) = t ;

or

I = eye(4) ;
  R = rand(3) ;
  t = rand(3,1) ;
I(1:3,1:4) = [R t]

Answer 2

[Guillaume]

The first concatenation is simply:

 [Rprime, tprime; 0 0 0 1]

The second:

[R, t; 0 0 0 1]

and so on.

[Nora Hora]

Thank you! And how would you save out the vector and the matrix from the result?

[Guillaume]

You're talking about Rhat and that, then:

p = [Rprime, tprime; 0 0 0 1] * [R, t; 0 0 0 1];
Rhat = p(1:3, 1:3);
that = p(1:3, 4);