Using mata to create matrix

[Weidi Hou]

I'd like to create a matrix shown in the figure. It's a NC*(N+C) matrix. All N block matrixes on the left are C*C identity matrix, and all N block matrixes on the right are C*N matrixes. For the block matrixes on the right, the 1st matrix has the 1st column of 1 and the 2nd matrix has the 2nd column of 1 and so on until the nth matrix with the nth column of 1 and all other elements are 0.

For example ,if N=20 and C=30, then the matrix is 600*50. then all 20 left hand side identity matrixes are 30*30 and all 20 right hand side matrixes are 30*20 with the corresponding column are 1. how could I create this matrix by mata?

[Niels Henrik Bruun]

Dear Weidi
No picture is attached.
For example purposes choose smaller to visualize.
However, Mata is extremely powerful when creating block matrices.
See -help m4_standard- and -help m4_manipulation-

Consider eg the Mata functions J and I ():

:
mata:
J(1,3, I(2))
       1   2   3   4   5   6
    +-------------------------+
  1 |  1   0   1   0   1   0  |
  2 |  0   1   0   1   0   1  |
    +-------------------------+

: J(1,3,(J(3,1,1), J(3,3,0))), J(3,1,1)
        1    2    3    4    5    6    7    8    9   10   11   12   13
    +------------------------------------------------------------------+
  1 |   1    0    0    0    1    0    0    0    1    0    0    0    1  |
  2 |   1    0    0    0    1    0    0    0    1    0    0    0    1  |
  3 |   1    0    0    0    1    0    0    0    1    0    0    0    1  |
    +------------------------------------------------------------------+
end

[Weidi Hou]

Hi Niels, thank you for your reply and advice. I uploaded the picture by pdf here.

[Weidi Hou]

Hi Niels, I used the I() and J() commands, they are really useful, thank you! But, as in the pdf picture, all block matrices on the right has different column of 1. If N are really large, typing the code over and over again is still a pain. Is there some simple way to do it?

[Niels Henrik Bruun]

Hi Weidi
I think this is what you need

mata:
: c = 3; n = 5

: J(n,1,I(c)), I(n) # J(c,1,1)
        1   2   3   4   5   6   7   8
     +---------------------------------+
   1 |  1   0   0   1   0   0   0   0  |
   2 |  0   1   0   1   0   0   0   0  |
   3 |  0   0   1   1   0   0   0   0  |
   4 |  1   0   0   0   1   0   0   0  |
   5 |  0   1   0   0   1   0   0   0  |
   6 |  0   0   1   0   1   0   0   0  |
   7 |  1   0   0   0   0   1   0   0  |
   8 |  0   1   0   0   0   1   0   0  |
   9 |  0   0   1   0   0   1   0   0  |
  10 |  1   0   0   0   0   0   1   0  |
  11 |  0   1   0   0   0   0   1   0  |
  12 |  0   0   1   0   0   0   1   0  |
  13 |  1   0   0   0   0   0   0   1  |
  14 |  0   1   0   0   0   0   0   1  |
  15 |  0   0   1   0   0   0   0   1  |
     +---------------------------------+

: end

[Weidi Hou]

Thank you so much! It is what need.