# st: Matrix problem

 From Eric Cahuzac To statalist@hsphsun2.harvard.edu Subject st: Matrix problem Date Mon, 21 Jul 2003 19:15:52 +0200

```Hi
Does anyone know how to solve this pb
Here is my data set (a sample)

+----------------+
| v1    v2    v3 |
|----------------|
1. |  2   100   101 |
2. |  2   100   102 |
3. |  2   100   104 |
4. |  3   100   105 |
5. |  2   100   106 |
|----------------|
6. |  3   100   125 |
7. |  2   100   131 |
8. |  2   100   138 |
9. |  2   101   105 |
10. |  2   101   106 |
|----------------|
11. |  3   101   125 |
12. |  2   101   131 |
13. |  2   102   104 |
14. |  2   102   105 |
15. |  2   102   106 |
+----------------+

a table of v2 v3, missing gives that

----------------------------------------------------------
|                       v3
v2 |  101   102   104   105   106   125   131   138
----------+-----------------------------------------------
100 |    1     1     1     1     1     1     1     1
101 |    .     .     .     1     1     1     1     .
102 |    .     .     1     1     1     .     .     .
----------------------------------------------------------

I want to obtain a matrix:

A[3,8]
101  102  104  105  106  125  131  138
100    .    .    .    .    .    .    .    .
101    .    .    .    .    .    .    .    .
102    .    .    .    .    .    .    .    .

where dots are replaced by corresponding values of v1

I try something like the following:

vallist v2, g(v2)
qui tab v2
global nbli=r(r)
vallist v3, g(v3)
qui tab v3
global nbco=r(r)

matrix A=J(\$nbli,\$nbco,.)
mat rown A = \$v2
mat coln A = \$v3

local i = 0
local j = 0
foreach k of num \$v2 {
local i = `i' + 1
foreach m of num \$v3 {
local j = `j' + 1
matrix A[`i',`j']=????????
}
local j = 0
}

Do you have any idea on how to cope with this problem?
Thank you very much!
Eric

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```