st: Creating a unique identifier from a string and byte variable

["Gauri Khanna" <gwkhanna@hotmail.com>]

Dear Stata List,

I am using cross sectional data with around 31,000 observations. I would 
like to create a unique identifier called "idchild" composed of two 
variables: caseid(string variable) and bidx(byte). I have described the 
variables below and listed them as well (observations, 29 & 30, 37 & 38, 960 
& 961 have the same caseid's but different bidx's).

des caseid

             storage  display     value
variable name   type   format      label      variable label
-------------------------------------------------------------------------------
caseid          str15  %15s                   case identification

. des bidx

             storage  display     value
variable name   type   format      label      variable label
-------------------------------------------------------------------------------
bidx            byte   %8.0g                  birth column number

. list caseid bidx

      +------------------------+
      |          caseid   bidx |
      |------------------------|
   1. |     2  1  66  4      1 |
   2. |     2  1  66  7      1 |
   3. |     2  1  93  7      1 |
   4. |     2  1 111  4      1 |
   5. |     2  1 147  2      1 |
      |------------------------|
   6. |     2  1 174  7      1 |
   7. |     2  1 201  2      1 |
   8. |     2  1 237  2      1 |
   9. |     2  1 255  3      1 |
  10. |     2  2  40  2      1 |
      |------------------------|
  11. |     2  2  65  4      1 |
  12. |     2  2  95  2      1 |
  13. |     2  2 105 11      1 |
  14. |     2  2 120  4      1 |
  15. |     2  2 130  4      1 |
      |------------------------|
  16. |     2  2 145  7      1 |
  17. |     2  3  13  2      1 |
  18. |     2  3  25  4      1 |
  19. |     2  3  55  2      1 |
  20. |     2  3  91  6      1 |
      |------------------------|
  21. |     2  3  97  4      1 |
  22. |     2  3  97  8      1 |
  23. |     2  3 121  6      1 |
  24. |     2  3 139  2      1 |
  25. |     2  3 145  3      1 |
      |------------------------|
  26. |     2  3 157  3      1 |
  27. |     2  3 181  3      1 |
  28. |     2  4  62  2      1 |
  29. |     2  4  89  7      1 |
  30. |     2  4  89  7      2 |
      |------------------------|
  31. |     2  4 116  3      1 |
  32. |     2  4 134  2      1 |
  33. |     2  4 197  5      1 |
  34. |     2  4 251  3      1 |
  35. |     2  4 260  3      1 |
      |------------------------|
  36. |     2  5 277  8      1 |
  37. |     2  5 413  8      1 |
  38. |     2  5 413  8      2 |
  39. |     2  5 429  4      1 |
  40. |     2  5 445  4      1 |
      |------------------------|
  41. |     2  5 461  4      1 |
  42. |     2  5 469  2      1 |
  43. |     2  5 501  4      1 |
  44. |     2  5 509  2      1 |
  45. |     2  5 533  2      1 |
      |------------------------|
  46. |     2  5 549  2      1 |
  47. |     2  5 557  2      1 |
  48. |     2  6  93  2      1 |
  49. |     2  6 159  2      1 |
  50. |     2  6 311  2      1 |
      |------------------------|
  51. |     2  7   7  3      1 |
  52. |     2  7  20  3      1 |
  53. |     2  7  85  5      1 |
  54. |     2  7  98  3      1 |
........

 959. |     2116  52  4      1
 960. |     2116  56  4      1
      |------------------------------------|
 961. |     2116  56  4      2
 962. |     2116  60  3      1
 963. |     2116  84  4      1
 964. |     2116 112  4      1
 965. |     2117  10  2      1
      |------------------------------------|
 966. |     2117  26  5      1
 967. |     2117  50  5      1
 968. |     2117  54  8      1
 969. |     2117  58  4      1
 970. |     2117  62  3      1
      |------------------------------------|
 971. |     2117  62  3      2
 972. |     2117  86  5      1
 973. |     2117  86  6      1
 974. |     2117 130  2      1
 975. |     2117 134  2      1
--Break--


I tried the following :

egen idchild = concat(caseid, bidx)
invalid syntax
r(198);

I realise that I am trying to concatenate two different *types* of variables 
and so I then tried the following:

decode bidx, gen(childbidx)
bidx not labeled
r(182);

Then I tried changing the caseid variable:

encode caseid, gen(childcase)

. des childcase

             storage  display     value
variable name   type   format      label      variable label
-------------------------------------------------------------------------------
childcase       long   %15.0g      childcase
                                             case identification

. egen idchild = concat(childcase, bidx)
invalid syntax
r(198);

How can I create a unique idchild? I am using Stata 9.2.

Thank you for your help.

Regards,

Gauri

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