st: choosing based on number of observations

[Michael McCulloch <mm@pinest.org>]

Dear Statalist members,
I would like to choose records in which the number of observations in 
a field, here named county, is greater than 5. Below is a tabulation 
of county. I've examined the help file for -count-, but this doesn't 
seem to suit my needs. Any guidance would be appreciated. Thank you.

. tab county

  COUNTY OF |
RESIDENCE @ |
         DX |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |         34        0.61        0.61
          1 |      1,055       18.78       19.39
          3 |         23        0.41       19.80
          4 |         11        0.20       19.99
          5 |          8        0.14       20.14
          6 |          3        0.05       20.19
          7 |        656       11.68       31.87
          9 |         53        0.94       32.81
         10 |          6        0.11       32.92
         12 |          4        0.07       32.99
         15 |          1        0.02       33.01
         17 |         38        0.68       33.68
         18 |          1        0.02       33.70
         19 |          2        0.04       33.74
         20 |          2        0.04       33.77
         21 |        174        3.10       36.87
         22 |          1        0.02       36.89
         23 |         10        0.18       37.07
         27 |          6        0.11       37.17
         28 |        104        1.85       39.02
         29 |         27        0.48       39.51
         31 |        102        1.82       41.32
         32 |          1        0.02       41.34
         33 |          2        0.04       41.37
         34 |        855       15.22       56.60
         35 |          6        0.11       56.70
         36 |          1        0.02       56.72
         37 |          2        0.04       56.76
         38 |        445        7.92       64.68
         39 |         85        1.51       66.19
         40 |          2        0.04       66.23
         41 |        430        7.66       73.88
         43 |        699       12.44       86.33
         44 |         27        0.48       86.81
         45 |          5        0.09       86.90
         48 |        362        6.44       93.34
         49 |        255        4.54       97.88
         50 |         22        0.39       98.27
         51 |          7        0.12       98.40
         52 |          2        0.04       98.43
         53 |          1        0.02       98.45
         54 |          3        0.05       98.50
         55 |         13        0.23       98.74
         57 |         54        0.96       99.70
         58 |         12        0.21       99.91
        230 |          1        0.02       99.93
        641 |          1        0.02       99.95
        999 |          3        0.05      100.00
------------+-----------------------------------
      Total |      5,617      100.00
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